My comp runs it (rather, CS:CZ, don't have CSS installed right now) on 60FPS (but my monitor is 60Hz LCD so I think it's forcing vertical sync) and steady and drops to 25-30 when there's smoke on the screen and it's pretty old...
You should be fine with a X1950XT
and an E6600, but I'm guessing your motherboard is Socket 478, so you might need a new one.. a stronger power supply might be required too. (you can give it a shot and see if it runs ok, and if not buy one)
I wouldn't buy relatively old hardware since it'll soon be rendered obsolete and you'll be sorry for buying it. (well, the new stuff too, but a year or two later..)
P.S. I think they were asking about your specs since "Some Compaq crap" doesn't tell us much about what it's compatible with, and we don't know if your RAM is DDR1 or DDR2, so newer motherboards might not be compatible with it.
In other words, you probably have to buy a new computer altogether. (one part isn't compatible with the other)