Now playing: Watch this: A look at the exciting new technology of Sony's 4K OLED...

LAS VEGAS--4K isn't just for wall-size, five-figure TVs anymore.

Sony is among the first major TV makers to announce it will sell 4K, aka Ultra High Definition (UHD), televisions in sizes less than 84 inches. The XBR-X900 series, which currently counts a $25,000 84-incher as its sole member, now includes 65-inch and 55-inch sizes, which sell for $4,999 and $6,999 respectively and are available now.

As of summer 2013, LG and Samsung now offer 55- and 65-inch 4K TVs too, although both are more expensive than these Sonys.

UHD/4K in this TV's (and most other's) case means a pixel count of 3,840x2,160 -- four times as many pixels as today's 1080p TVs. The advantage, according to its proponents, is an even sharper picture. One problem, according to us, is that you'll have to sit very close, especially to a screen this small, to appreciate the difference (see our in-depth look at the 84-inch Sony for more). There are many other issues, too, to the extent that we currently consider 4K TVs pretty stupid.

To its credit Sony is starting to address one big problem, lack of content, by selling a 4K video player. I also applaud Sony's decision to buck the "UHD" moniker in favor of the more established, and frankly catchier, "4K."

Aside from 4K, the XBR-X900 is packed with picture-quality enhancements, but it lacks the most important one, in my opinion. Unlike the 2012 XBR-HX950 (which will remain on sale), it doesn't have full-array local dimming. On the other hand, its edge-lit display does include edge-lit local dimming ( more info ), which in Sony's implementation works better than just about any other example of its kind, judging from models like the

The company's press release spends a lot of ink praising other picture-quality enhancements, like 4K X-Reality Pro processing (it had better be good to upconvert all those 1080i/1080p sources to 4K), a wider color gamut (not that interesting if you want accurate color), and what Sony calls "Triluminos Display LED backlighting." I double-checked and no, it's not the same as the three-color LED backlight of the vaunted XBR8 from 2008. Instead it promises more color improvements, and judging from our review of the similarly equipped W900A, that promise holds water to some extent. Check out our in-depth look at the technology for more nuts and bolts.

You may have also noticed the honkin' speakers in the picture gallery above. I'll let the press release handle that: "Utilizing a Signal-to-Sound Architecture, these TVs incorporate Sony's own magnetic fluid speakers and unique digital signal processing technology to deliver smooth midrange, lower vibration, and deep bass. The front-facing speakers on XBR 4K LED TVs extend Sony's new design concept to match the exterior aesthetic of some of the other 2013 models for the home with a striking, angular, faceted outer cabinet -- incorporating the Sense of Quartz design concept." They most likely won't be removable.

The XBR-X900 also offers all of the features of the step-down sets like the R550A, including NFC and RVU (click through for an explanation). Beyond those fancy extras is a full helping of Smart TV, including the Sony Entertainment Network of course, and the company says the interface has been improved (it needed it).

We'll have more information when we can get our hands on a review sample.

Updated April 10 with official pricing and availability information, and July 15 with additional developments.