Based on your system, I think you should instead focus on how much power you will need to adequately drive your ET LFT's. I vaguely recall that they are not terribly efficient (84-85 db?), so they will need a fair amount of juice to play at high volume levels. While it's true that the center channel carries most of the dialogue, it does not normally handle low frequencies (many center speakers cut off at 80-100 Hz).
You have correctly noted that there are two schools of thought on power supplies for multi-channel amps: one large supply for all channels, or separate smaller supplies for each channel. Both design approaches have proven to work well, assuming the manufacturer executes the design properly.
I am personally of the persuasion that separate power supplies provide somewhat better sound quality, and therefore I use a Bryston 5B-ST (150 wpc, 3-channel) amp for the center speaker and rear surrounds, and the more powerful Bryston 4B-ST (275 wpc, 2-channel) amp for the main speakers (which have flat frequency response down to about 26 Hz).
For home theater use, I think Bryston makes a nearly unbeatable line of stereo and multi-channel amps (and a very fine pre/pro). And if you also use your system to listen to music, then the Bryston amps are a particularly good choice for dual duties.
