Yes sir, I can help you. (maybe) I too was having horrible FPS problems. I have a QUAD Core 6600 overclocked to 3 ghz. I have 4 gb's of quality ram. I have one of the fastest Hard Drives known to man. I have an ATI Radeon 4870 card. (not the latest or greatest anymore but still one hell of a video card.
My point? My computer (I built it myself) shouldn't be slow at ANYTHING. It should be blazing fast and it always is. Except for SH5. I posted this thread here :
http://www.subsim.com/radioroom/showthread.php?t=180090
And I got my answer. Someone said to turn the shadows down or something and I did and my problem was fixed. Hope this helps.