I don't recommend using hardware mode, especially not with a powerfull PC like that. HW mode even disables some effects. Funny fact, my P166 MMX was able to run Software mode at a decent FPS.

That your FPS is locked at 59 and 60 FPS is not so strange, your monitor is (most likely) capped at 60 hrz. Mine hits at 120 FPS because my monitor is native running at 120 hrz

However, there is away to overrule the 60 fps cap but i'm not sure how that works.