Hi guys, I'm not sure this is the right place to ask, but...

I've got a Core 2 Quad Q9400 @3.2GHz (2,6GHz stock) on a P35 board , 4GB ddr2-800 low latency memories and an ATI HD5850 @800-1200 (725-1000 stock) with 1GB VRAM

That is capable of running vanilla skyrim at high settings @60fps in quite every circumstance.

Following the "baseline" ("performance" for the heavier mods) configuration from the STEP guide It can run @30-35 fps. Using the Skyrim performance monitor I can see that the CPU is always under 50%, no more that 2GB ram are used, but the GPU is always at 100% GPU and 100% VRAM.

I'd like to go further in modding the game, so I'm guessing if a better GPU could help. Would it be reasonable to pair a better GPU to that Hardware? What's the best GPU that could fit it.

Do you have any suggestion ?