Me personally, I like the new version better, the top image isn't a dominant anymore compared to the other one. About not supporting 800*600, I wholeheartedly agree ^^ My motto is "Stop living in the past and upgrade your monitor" Some people are just to stuborn if you ask me and need a wakeup call...
The centered "to be or not to be" is kind of personal preferance. I like sites which are able to have their contents fillout the sitespace to not leave any "blank" areas (like this forum for instance).
If a site isn't able to do this, usually sites using a static layout with a set width, I'm guessing it's what your site is going to use. It's better to center a site on the page, to balance things out.
It just doesn't look that good on 1280*1024 or above (even 1024*768 in very "thin/tall" sites) when a static layout site is cornered on the far left or right just to leave a large open space on the other side of the page. It could work for some site designs, but IMHO it looks bad most of the time.
However as I said, it's still personal prefereance though. The overall darkness of the site in combination of the black background could push this "wide open space" into the background. And that would make your site fall into the category of "some site designs" ^_^ You could even try and create a background image watermark or something break up the flatness of this open area (think TSA/Kaahra logo) Or as some sites do. a 1x2 pixel *.gif image, with 2 black colors (one a little bit edging towards grey). In effect creating vague scanlines
But now I'm meddling in your site design, so I'll stop here