So um...apparently FF7 Crisis Core for the PSP isn't Vaporware.

The X1950 Pro does seem to be the best card at that price range from what I can tell (good job in researching that). I've seen some places offering X1950 XTs for $250, so if you're willing to pay the max amount you gave, that might not be a bad option. Here's a link from Newegg:
http://www.newegg.com/Product/Product.asp?Item=N82E16814102067

The XT has a decent boost in performance over the Pro, so it might be worth the extra $50 for you...or maybe not. If you want to look into it, I can give you some benchmarks of the two cards.

That said, you might want to look into waiting. If I'm not mistaken, ATI's (or...um..AMD's) response to the Geforce 8800 should be out sometime next quarter (rumored to be launched at the end of January IIRC). That will be the new top-of-the-line card from ATI/AMD (and possibly/probably the top overall). There will probably be some price drops around that time for some of the cards being "pushed down." That might depend on the availability of the new cards though...ATI usually has issues with availability.