If you care for loading times in games, more RAM may indeed be the way to go. I remember older reviews from times when 2GB RAM were no benefit for games in general (except for MMORPGs like SWG), but loading times improved across the board, though sometimes by a small margin. I can't remember any recent tests on this, so I don't know if 4GB would give you a benefit now (maybe only on Vista64?).
For the paging file, it may theoretically give you benefits to put it on a second drive, but I doubt they are noticeable, especially not in games/loading times. There is always some paging, true, but as long as you have enough RAM, it won't hurt. If you put the paging file on a second drive, it would have to be at least as fast as the first drive.
The old raptors are slower than the new WD drives, so I wouldn't consider using them at all. A 250GB/platter WD SE16 already beats even the best variety of the 74GB raptor, which was noticeably faster than the 36GB model, and the 6400AAKS' perfomance (320GB/platter) should be better and match the Samsung F1 1TB or even the WD 1001 1TB (which are in the database, the 6400AAKS is not): SR-Comparison.
Bottom line: Go with one 6400AAKS. Plus some RAM, if you need it.