CPU power makes a huge difference... I just upgraded to a new E6600 core 2 duo and I'm getting about two to three times the frame rates I had with my old AMD 4800 X2
edit: Just like to add that Suikoden IV is actually semi-playable now, whee!
Intel Core 2 Duo E6600
2GB DDR1 3200
256mb eVGA 7800gs