z506 seems to have very nice configuration. T6200 is weaker that this, but i am not sure about the sound quality.
I have T6100 bought about 2 hrs ago, and i still think it sounds good. also 26w subwoofer is very good for a single room - as long as the sound is tight.
don't forget to spend some money on a good sound card. and try to protect the speakers from dust at all costs !