I've pasted the mod load order below but in sum, I am running every DLC except zeta, FWE, Fellout, MMM, and the Wasteland patrols mod.

-FWE doesn't take up much performance aside from new textures, armors, weapons, etc.
-MMM takes up performance because I have the Increased Spawn settings to 2-4 and no 'reduced wasteland spawns' selected in it.
-Fellout is enabled, but I've never been sure if this is a mod that causes perf issues or not.
-Enhanced blood textures, which I assume must have an effect on performance because of the huge size of the splatters.
-MTC Wasteland Travelers also adds a sizable group of NPCs to the Wasteland because I have set the ingame tool for it to produce lots of spawns.
-Wasteland Patrols (see here for a description on what it is: http://www.fallout3nexus.com/downloads/file.php?id=11729 ) settings are set to:

set mbQuestSpawnInterval to 20
set mbSpawnConflictChance to 100
set mbSpawnGroupChance to 50 (default)
set mbSpawnChance to 60

This takes up the most performance because it's adding an amount of actors to the wasteland that the game was never really intended for. There are real, dynamic fights in the wasteland and with FWE combat settings it's a grueling existence.

Now, here's my problem though. I really don't want to lower any of my primary mod settings. I want to keep this setup. But it comes at a major cost. I recently upgraded my graphics card from a 9800GT to a 470GTX, on the advice from some here that it was GPU causing crashes and slowdowns. The slowdowns are mostly gone, and performance is a lot better with the 470GTX. But some of the problems remain nonetheless:

-2-3 second freezes (happening twice one after the other) after every time I load something in the distance, like the Fairfax building towers or Tenpenny towers (which -sometimes- causes a crash or a lock-up/full freeze that I have to manually restart from)
-Random crashing. It could happen when I'm in an interior with abseloutely no lag whatsoever, or in downtown DC where there's raiders/mutants/talons all fighting each other at once.
-Anytime I die, unless it's in an interior, my game crashes and I have to restart to load. I'm assuming this is because it has to 'forget' the amount of NPCs in a certain area and load the quicksaved state, but I can't be certain.
-If I ever see a group of NPCs added by Wasteland Patrols enter an interior, like a Metro/sewer or something, my game crashes right after the engagement. A couple times this didn't happen but it seems to be consistent for the most part.

These problems aren't 'constant.' The game is playable under these conditions, but the crashes are aggravatingly random. For example I cleared out evergreen mills yesterday, we're talking about maybe 30 or more raiders in the outside perimeter plus the big guy in the cage, and once I finish looting them all I crash. And then find out that I hadn't saved after the battle. While I was down in the canyon I could hear gatling laser and other gunshots coming from above the canyon so there was another battle going on too at the time.

My graphics settings are not on max. Water is taken down a bit, although I'm not really close to water most of the time. Shadows are completely disabled. Vsync is off. Antialiasing is 4x, and anisotropic is 8x. Resolution is 1900x1000 abouts. The only 'ultra' setting that I keep is the view distance of objects and NPCs, because it's really stupid to run a mod that populates the wasteland and makes it dangerous only to be shot at by invisible NPCs who are beyond your view distance (and then you cant fight back).

My system specs are the following:

Windows XP
3.2ghz AMD Phenom II X4 Black Edition (Quad core)
4GB RAM
470GTX graphics card
320GB WD hard drive
Corsair 650W PSU (the highest rated one on newegg).

Lastly, I'd also ask those tech gurus on this forum as to whether or not this is something that can even be controlled by better performance. My 470GTX has no problems with any other game. The reviewers on newegg for the card even remark that there is 'nothing they can't throw at this card.' Yet fallout 3 chokes and crashes with some extra NPCs. Why is that? Is there a limit? A point to where the game automatically closes out if too many NPCs are on screen or in visual distance?

Thanks again.