Skyrim modding (S.T.E.P) for low-end PC

I am currently modding skyrim using S.T.E.P (Skyrim Total Enhancment project).

The thing is, my computer is getting pretty old.

My specs:

AMD Phenom 955 4 core 3,2GHz (Overclocked to 3,8 using preset)
Fractal Design Kelvin s36 360mm cpu cooler AIO
Asus M4A77T motherboard
Asus EAH 5830 GPU
Corsair Force Series LS 240GB SSD (Sadly my motherboard only supports SATA-2...)
4GB (2x2GB) 1333Mhz RAM Dual Channel

Yesterday I installed up to the E.2. Interface mods. I did not install Wrye Bash or DDSopt. I used Skyrim Performance Monitor and I was getting steady 50fps, a bit lower than vanilla, but gameplay and camera movement was actually smoother. After I installed 2.F. Conflicting Graphics sections I was only getting around 30 fps with drops as low as 10 fps. Heavy "macro stutter" (I think it is xD), camera movement was very laggy.

I installed the core and extended mods. I know I messed up some things and tried to fix them later (Not sure if I did), im thinking about just doing a clean install again, with only the core mods and the lower quality baseline where available. Then once im finished I can try to optimize it as explained at the bottom of the wiki (DDSopt etc).

Im guessing I shouldn't even bother installing the Flora Overhaul, since its heavy on performance. Any reccomendations, mods I can skip without interfering with other mods?

Anyone that has experience with S.T.E.P on a low end system?

Edit: What I really want to know, what resource heavy mods should and can i discard from the guide without messing things up?