Also, the FPS often starts out at about 21fps, then suddenly jumps to a smooth framerate about 3 or 4 seconds after a loading screen.

Been looking online for comparisons, but all of them are for pre-optimized skyrim.

Currently at the latest patch, my game runs from about 35 fps (whiterun steps) to 60fps (lookin down or up wherever) with vsync on, FXAA Post process injector, Skyrim HD Lite and a few other mods, like WATER and Realistic Combat.

I have a Phenom II X4 at 3.4GHz and 4GB ram on Windows 7 64bit.

I run Threatfire, Comodo Firewall and Avast Antivirus.

My 3Dmark 11 score is P3658

I vaguely remember being able to run an ENB at about 30-40 fps but thats when I had a smaller screen (1280, 1024), but I dunno what happened to that one, now I can really only rely on FXAA. thoughts?

That's to be expected. Your CPU is the bottleneck, which is why your FPS is lower in cities.