@Dan: Because the A2000 is the size of an aircraft hanger, and the A4000 case is really cheaply made, but the A3000 is a slim good looking machine :-)
Plenty of dead ones out there that can be used ...
@Mad: Any 16-bit soundcard should sound exactly the same through WinUAE, the graphics is only on 2D performance, so an 8x AGP card would give only slightly more performance over a 4x one (ie. an ATI XPert98 is 99% as good as a much newer card) - ATI cards all run cooler than NVidia ones, which may infuence your choice.
For UAE performance the performance is better spent on a faster processor rather than fancy graphics/sound ...