Sprint just officially announced the HTC EVO 4G LTE , which is a variation of the HTC One X announced at Mobile World Congress, plus a few little surprises. The key differences? A stylish makeover headlined by a red kickstand, a new Sprint service called HD Voice, a MicroSD slot, and a switcheroo from a Quad-core Tegra 3 to 1.5Ghz dual-core Qualcomm chip.

From a pure spec standpoint, the Evo 4G LTE is somewhat of a beast. It’s got a 4.7-inch screen HD Super LCD screen that is both humongous and gorgeous. Somehow they pack this huge display into a device that manages only .35-inches in thickness, 4.7-ounces in weight, yet somehow comes equipped with a 2000mAh battery. That’s a power combination.

While Sprint’s take on the One X doesn’t include the Quad-core Tegra 3 processor, the switch to the dual-core Qualcomm chip was necessary to allow 4G LTE support. Don’t be too bummed: tests have shown that this alternative performs just fine. Couple it with 1GB RAM and you’ll have no problem running Android 4.0 with HTC Sense 4.0 smoothly on your Evo 4G LTE.

Another change from the European version comes in the storage department. While the One X doesn’t have any external storage, the Evo 4G LTE has a MicroSD slot you can access by snapping off the top part of the phone’s rear. Almost like removing the battery door, but with the Evo 4G LTE the battery is not removeable. I don’t mind this as HTC’s unibody form provides minimal size, maximum battery savings, and a sexy sleek look.

You’ve also got 16GB of onboard memory, so media mavens will have plenty of space for music, movies, games, apps, and every other form of entertainment known to man.

Let’s talk about that sexy sleekness for a minute, because boy oh boy, the Evo 4G LTE is a looker. It’s standout style is sure to draw it’s fair share of lovers and haters, but you can’t argue that the device stands out. The red kickstand and red camera ring give the phone a very strong, dynamic look. It’s uniquely Evo in a day and age where uniquely designed smartphones are few and far between.

I’m also a big fan of the Evo 4G LTE’s rear being two-toned – with glossy plastic above and matte looking metal below the kickstand – but that uppger glossy plastic is a magnet for fingerprints. Case and point, check out the phone’s rear after only having touched the phone for 3 seconds (to turn it over):

Our readers were quick to point one potential pitfall of the Evo 4G LTE’s kickstand: it may be difficult to charge via MicroUSB while the kickstand is up because of the positioning of the kickstand in relation to the port. The kickstand is supposed to be supported in three different positions, which would render this complaint moot, but more thorough use of the device would be required in order to make a judgement.

Before rounding out the rest of the specs, let’s take a quick look at a feature Sprint is calling HD Voice. This is the first ever device to have HD Voice, and when I first heard the feature announced, it seemed like another PR-ish attempt to pack bold specs into a growing list of proprietary technologies that companies wear as a badge of honor. But don’t assume so easily- I tested the Evo 4G LTE HD Voice feature first hand and it absolutely makes a difference.

The test took place across two audio booths. I had the original Evo and the Evo 4G LTE in my booth and a Sprint rep had both phones in a separate booth. First we talked on the original Evo. Exactly what you’d expect. Then we talked on the Evo 4G LTE and… wow. I was pretty floored at the difference. Much more crisp, much more clear, almost to the point of sounding a bit fake, as if you’re listening to a television broadcast.

Then the Sprint rep turned on music. Loud music. Using the Evo 4G LTE I couldn’t really hear anything in the background. Switch back to the original Evo and… wow. Lots of noise. Turns out that Sprint’s HD Voice is much more than just a line in the tech specs. It greatly improved both audio quality and noise cancellation in a very obvious and welcoming way. Unless, of course, you actually want the person to whom you’re talking to hear something you’re playing for them in the background. Then it’d be a bit of a problem.

Moving onto the dual-cameras on the Evo 4G LTE, we’ve got a rear facing 8MP camera and 1.3MP front-facing camera. Like many others, HTC now has a quick capture capability which is nice (watch the video test from MWC), but as with the One X they’ve done away with a toggle between pictures/video mode. Now you have both a picture shutter and a video button on the camera UI, stacked on top of each other, allowing you to take pictures even while you’re recording video.

This is a great feature. I often find myself in the precarious position of deciding whether to snap a photo or grab a video in hopes of capturing that Kodak moment. The Evo 4G LTE camera allows you to capture both simultaneously, but I imaging pictures taken while filming video are merely screen caps from the HD Video. Still, in my opinion, a great feature.

Cutting edge techies will be happy to hear the Evo 4G LTE has NFC (Near Field Communications), which allows users to make payments with the swipe of their phone using various apps. While NFC has yet to gain widespread use amongst retailers, we’ll likely see higher rates of adoption over the next couple years.

As with all of HTC’s new handsets, the Evo 4G LTE comes with Beats audio, which provides enhanced audio integration across all features of the handset. Of course you’ve also got your typical smartphone standards such as 3.5mm headset jack, Wi-Fi, Bluetooth, GPS, and all that good stuff.

Prior to the announcement of this phone, everyone thought Sprint would unveil the HTC One X with a few slight changes. That’s exactly what happened, but I have to say the changes – both in style and specs – had more of an impact than I imagined they may. The red accents give the phone a uniquely Evo taste, the HD Voice quality is fantastic, the MicroSD slot is essential, and the kickstand is an added benefit many will enjoy. The swapping of processors may leave some tech enthusiasts yearning, but regardless, the Evo 4G LTE will immediately become one of the most powerful and well rounded mobile phones to hit the market.

The Evo 4G LTE will be available for pre-sale on May 7th for $199 but an actual launch date is still too be decided. We invite you to visit our HTC Evo 4G LTE Forums where it seems a loyal following has already gathered.