No. With NVIDIA's naming system, the higher the number, the better it is (although cards that have a prefix like GT and GTX are higher than simple numbered series).
no not at all 8800GT is better
it will never be GeForce 8400 is improved and and is better than GeForce 6800 in every way
It's much better than the Geforce 2, and probably on par/ slightly lower in speed than the 6600.
No.
XFX - Better warranty, more well known, also more likely than not factory overclocked. If not check warranty but I believe XFX is better. Also consider the bundled game if any.
The GTS 250 is much better. The GTS 250 is similar to a 9800 GTX.
I've tried it with games such as COD5 and others and can say 8400 is not as powerful but looks better 7600 can handle more so is better for games
The Nvidia Quadro. Although there are much better options out there than the ones you listed me.
Yes by a long shot
Normally the 6000 GT would be, but the 9400 GT a lot Newer than the 6600 so its overall faster.
ATI is the older company (1985) than Nvidia (1994). However there was a time, about 1999-2002, where Nvidia singlehandedly dominated the 3d graphic card market, ATI sort of "came back" from that, and is head-to-head with Nvidia today.
the 4330 newer anyway, should be better, nvidea recomende is more marketing than fact, although I do preffer nvidia cards. Do not waste money on an old card like a 7900 gt tho, for the same price you can get a GTS 250, but wait is this for an Mac book? then sure go for the nvidia