Given time and enough posts about this, someone will find a solution. It is amazing what people are doing, like the falling autumn leaves, the accumulating snowfall, OBGE shaders. Truly amazing. I may play Skyrim once or twice when it comes out, but there is much left to do in Oblivion, so expect to be back to it.

EDIT: That is, of course, unless it gets modded as much as Oblivion is

Woops, forgot to report back.

So I am basically now back to a mod setup that is exactly the same as in the OP, except MMM (and I do mean everything in the first post; Qarl's, RAEVWD yadda yadda, the whole bunch), and finally with reflections turned OFF.

I get a consistant 30 FPS average (can't go higher due to OSR) while running around in Tamriel and in dungeons, but in some fights when there are a lot of enemies, especially outdoors, the FPS can go below 30, but never below 20. I find this playable enough.

I haven't messed around with MMM yet because there are so many optional plugins. I actually want a lot of the extra stuff but I need to test them all to find out which of them are the ones that drain the most FPS and see if I can do without them. I'll also need to try all of the reduced spawn plugins (there are many versions) to see which one reduces the enemies just enough to let the game maintain a smooth average, but not cut down on the enemies too much that it starts to feel really bare - because if there's going to be sparse enemies, I might as well just play vanilla. The whole point of me modding is to get more action out of the game. Plus very sparse enemies will make my character progress slower due to lack of experience points.

So the final word for now is... I have deduced that with a setup like mine, even water reflections can be too much and is the one that contributes the most FPS drain, especially outside and at the IC Waterfront.

Hopefully this thread will be a useful source of information for users who would run a search on FPS issues in future.

(oh and here's keeping my fingers crossed that when OBGE eventually has replaced water shaders, like what MGE is doing, it won't hurt FPS as bad as the game engine's internal water system...)

Oh i have the same proble one time!

But without that computer... For me 30-25fps was fine haha

The good news, is not a problem of graphics mods... So you can keep using all of your hardware power (I have the same problem inside the dugneons 1-5fps so... I unchecked all my mods and i checked one for one to get the conflict) The conflict was between OOO and MMM (i never use Franchesco's mod so i can't tell you if if it have a problem too)