[gtMc]

Update. Got the E85 amp into the back of the car today. Install was quite easy. The quick answer: It makes a BIG difference, and there is a BIG improvement. This is a great, cheap solve.

The more winded version:
Before doing the swap, I listened to 4 different songs, each thru the CD player and also thru my ipod via the aux jack. My neighbor and my wife also listened taking turns in passenger seat. SO, our baseline is now in our heads.

Then I swapped the E85 amp into my E86, and listened to them all again.

I did this three times, with doors/hatch closed, engine off, DSP set to Jazz (recall I have no navi), bass flat, treble +3 clicks, balance/fade all neutral, and speed volume control set at 1.

Each time, we all noticed the same changes. Much clearer, harder hitting, virtually no fluttering or "blown speaker cone" sounds, and overall capable of much louder volumes and while staying remarkably clear. I will say with this E85 amp, its now one of the better if not the best sounding stock system I have heard in a BMW.... with my wifes X3 with underseat subs also ranking right up there. (I havent hear an Alpina B7 to comp, sorry). I know, it's still not a $4000 aftermarket system. But it sounds darn good and very impressive.

My expectations were high, and I didnt want to be swayed by a hope or placebo effect, hence bringing 2 more listeners in and doing it 3 times over. Bear in mind I'm not an intense audiophile or a pro-critic, just someone looking for a good sounding system, and this did the trick.

MHeavNC's thread "working with carver subs" (link above) explains it all, he's the one who stumbled on this - well done man!