Hell, you can prolly get a Matrox g450 on Ebay for 20 bucks. They work great for trading, but probably few PCIe cards around. They make em in PCI and AGP.
Charting is not data intensive at all (as compared to graphics). Just about anything works well, unless you go to large monitors which require high res.
I am currently using a discontinued Matrox Geronimo Pro quad, which has never had any problems with four 19" monitors at 1280 x 1024. I gave my g450 dual to a friend who is running it fine on a win 98 system! He runs two 19" monitors with a live forex feed. Seamless. His system is prolly worth about $200.
Most traders go way overboard on the system. Unless you are already profitable and expanding, I say go the cheap route. Works just fine.