you have missed out man
X850 is old hat now, and dare i say it was kinda old hat when it came out because nvidia's offerings had alot more features to offer. the X850 did have some good raw speed though.
but since then theres been the almost still birth (because it was so late) X1800 which brought ATi into the SM3 arena and a very few short months later came the current daddy of single GPU cards.... the X1900 series (lately just refreshed as the X1950)
all you gotta do is compare the specs
X850XTX
*16 pipe lines with 16 pixel shaders, 8 vertex shaders running at 540Mhz
* 256bit memory using GDDR3 (1100Mhz?)
* extended Shader Model 2 capabilities
* the usual ATi impeccable Image quality
* cross fire . though it was limited to 1600x1200
the X1900XTX
* 16 pipe card, but with 3 pixel shaders per pipe giving 48 pixel shaders. 8 (or is it 10?) vertex shaders running at 650Mhz
* 256bit GDDR3 memory running 1550Mhz
* shader model 3 support (some claimed not full since vertex texture fetch was missing....like it mattered) along with the ability to use FSAA with FP16 HDR lighting effects
* even better IQ
the x1900 is way way way faster than the x850 and its got more features.
http://www.tomshardware.co.uk/graphics/charts.html
check that link out, toms hard ware guide, although not very popular at times, do have a good graphics round up. it should show you how your X850 compares. when you use the charts be sure to select a higher resolution and AA and AF settings to get a better picture of jus how much better the x1900 is
and they had your eyes out if you paid $500 6 months ago.
goood example
http://www.tomshardware.co.uk/graphics/...elx=33&model1=565&model2=548&chart=199
HL2 episode 1 1600x1200 4xAA 8xAF the X1900 is over 2x as fast as the X850