My setup is an Intel Core 2 Duo OC at 3.6, 4 gig of ram, and a nvidia 570 OC to 800 and 2000 for the mem.
I would like to run the DLC HD pack and wondering what would be the best performing ENB out there, as I don't have enough vram to run anything extreme.
Any help would be appreciated, thank you.

your specs are a slight bit better than mine (you cpu and video card are slightly better) and i run a combo of RCRN and Enhanced Shaders FX ENB (slightly tweaked) I also run the dlc hd pack and many other texture packs (dont go over 1024 for most, armors and weapons are an exclusion) and my game is fairly playable, i get slowdowns but thats most likely my cpu bottlenecking.

I would say try some out and see how they run.

Also i highly recommend using http://skyrim.nexusmods.com/mods/9080 if you get the dlc textures. It gives you 3 options of how to optimize it.

Just pick whichever ENB you like the best and disable the SSAO using the enb.ini that will give you a huge performance boost.

Running SMAA injector instead of regular AA will give you a ton of extra vram/gpu back as well at the cost of a slight texture shimmer in some situations.