most important factor for pcsx2 is the cpu, a core2/i7 at 3,2ghz is recommended and afaik this game is one of the most demanding in pcsx2 at the moment. if you try sw mode, then set your sw threads in the gsdx config to 2 or 3, anything more will probably make it even slower. but update your pcsx2 and plugins to the latest beta revisions from this forum first. and try some more aggressive speed hack settings, but if your gpu is the limiting factor in this game, then it probably won't help you that much (if the cpu usage shown in the pcsx2 title bar is constantly at 90%+, then it's your gpu).