OK, finally got my 2GB HyperX module, which was shipped 3 friggin days late. To my delight I found I can still use triple channel config by putting two modules side by side in the first two black and blue slots, and each of the other two in a blue slot.
Initially I got the same problem I was having before, lots of pauses. Then I reinstalled the game and for some reason this time DirectX added some updates, instead of saying it was already up to date like before. So I went ahead and did a repair on the few C++ Visual redist files as well just in case.
It then ran so well I bumped everything to max with internal VSync and external 2xEQ AA, but shadows dropped to 4k and Depth of Field at medium and Haze Flares off. Still I was getting a fairly solid 60 FPS. There are times though when grinding perks on the easiest mode when drawing tons of fire from several AI it will start lagging bad. So I guess I've not yet found the ideal settings.
I think I'm going to focus on textures and leave them maxed, and even set a 16x command for AF. I've also tried using D3DO for VSync and triple buffering, and dropping the AA in CCC to 2x without EQ. It's helped some. Does anyone know a way to turn Depth of Field completely off though? I'd rather not have any blur at all.
Anyways, just glad to have it running better now. I don't get the big pauses just moving around anymore, and the lag I did describe may have been partly due to reloading the checkpoint several times to get certain perks I was going for. The odd thing is, when I got the perk that requires using dual wield rocket launchers, I stormed the U-Boat area where you drop down from a vent in the ceiling and all hell breaks lose, and there I didn't get the lag. That may have been after I went to external VSync and 2x vs 2xEQ AA though, don't recall. I was up so late I wasn't thinking straight. The area where several AI were shooting at me did involve a troop at a fixed turret and lots of shader effects with fog and/or dust though. It's the spot in the first level where you blow the big door and come upon a lot of Nazis in a train tunnel.