It depends on the breakers for the circuits...I assume that with a 240 volt mains, it would be be connected to a 50 amp breaker.....so that means that the mains will dump 240 Volts at 50 amps...ie 240*50 Volt Amps....or 1200 Volt amps...ie 1.2KVa....if the breaker was a 30 amp breaker off your mains then it would be 240 Volts times 30 Amps to equal 720Volt Amps or 0.72KVa.....

That means that with the same voltage ...bigger breaker is better....so 50 amp would be better than 30 amp....now comes the safety part...

In order for the TRANSFORMERS to handle MORE AMPS they have to be bigger (the weight of the metal has to be bigger ....that way it doesn't over heat (the metal in the transformer can distribute the heat better if it is more massive...more surface area to get rid of the heat faster and more volume to take up the created electric flux field....

Also the wires need to be bigger to handle more amps....there are rules of thumb, but if you get 10 gauge wire...and just make sure that it doesnt get much hotter than will burn you, then you should be okay...you just make sure to turn it off before it gets that hot....(also remember that just because the surface is not hot enough to burn you doesnt mean that the wires in the inside of the transformer (the ones you cant touch) are not getting hot enough to burn you.

The heat burns through the insulation creating a short so dont destroy your transformer by letting it get to hot...

there is much more too it, but hopefully that helps....

more transformers are better than less....and also if your stick wont start an arc, then it is likely too low of a voltage (so add another transformer in series....and if

the welder sounds more like it is cooking bacon in grease, then that means that your amperage is too low for what you are welding...so increase it...(one way to increase it would be by using less wraps of thicker wire...

good luck man.