Why arent you thinking about the x1800xt 256? Same price, but beats them all except the x1900xt. If you want to spend $270, get the x1900xt, but if you want to stick closer to $200, then i say x1800xt.
Also, the 7800gtx and the 7900gt usually split wins if i remember correctly. Also, you should be able to get a 7800gtx for cheaper than that on the forums.
A highly OC'ed 7900GT will beat an X1900XT at stock speeds in some benchmarks & come close to it in most others, but once you overclock the X1900XT it has the advantage again & most XT's are decent overclockers as well.
If you can get an X1900XT for $270, jump on it ... thats a great deal!
the 7900 gt's can gt to gtx speeds withvolt mods and volt mods only and some additional coolig.
The x1900 xt is good to overclock with until about xtx speeds plus 10/15 more on core and mem.(on stock cooler)With different cooling the story might/will be different.With the prices u mentioned the x1900 xt is the best buy.(HDR+AA,HQ AF,what more do u want for $270?)
Enough said, If I had to choose:
1900XT>7900GTX OC>7900GTX>any 7900GT
If you get 1900XT for 270$ and 7900GTX for 250$(which you won't), get 1900XT. 7900GTX>7900GT PERIOD
Highly volt modded overclocked 7900GT > 7900GTX by a small margin but is unnoticeable and won't be so in the near future due to lack of 512mb vram, therefore there is practically no point getting 7900GT + all that cooling and seeing no difference over 7900GTX. And once you overclock 1900XT, there is no match.
I repeat 1900XT and 7900GT are in a different league.
7900GT: performance mainstream
1900XT: high end and 1900XTX too
1950XTX: ultra high end
classification in terms of performance
like i said earlier the x1900 xt isn't the most overclockable chip out there.It's already near the limits at stock.U can get it to xtx speeds + little more,thats it.Regardless of cooling solution.
But for the prices he mentioned the x1900 xt is a steal.
As for heat, I've got my X1900XT in a SFF, so the LANBoy should be able to handle it (which I've got too, but it's in storage). Just make sure you clear anything you want to keep away from the exhaust duct - when I tried out the Auto OC feature in ATI Overdrive, it felt like a heatgun back there (and I thought the air coming out of the NV5 R3 on my 7800GT was hot...).