its funny reading back through all this that ATI really is in a pretty clear lead. Nvidia has the 280 now which has the single fastest GPU, but the ATI 4870 X2 has 2 GPUs on one board. While you can SLI 3 280s together, they arent much faster than 2 4870X2's in crossfire. ATI's big advantage is that theyre quite a bit cheaper for the speed you get.
Also PJ it wouldnt cost too much money for you to buy a halfway decent videocard, which might not be a bad idea because i think thats the only thing holding you back from TF2 on your computer now.
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"All the world's a stage
And all the men and women merely players;
They have their exits and their entrances,
And one man in his time plays many parts."
- William Shakespeare's "As You Like It"