Hey buddy! Refresh my memory on what your exhaust set up is currently. What is your desired sound. I've put in few hundred on a few variations (and it's still a work in progress) with one constant. I have kept the factory middle muffler. So let's start there. Drone has been the issue I hate most. With the 5M transmission, your going to be better off during cruise situations due in part to a higher cruise rpm. Your going to be out of that 2000-2600 range that I/we tend to have drone issues. That makes your options easier. I like your choice of the Borla proxs dual in dual out for the middle replacement. I have been considering that one for some time. It has the integrated x-pipe. Performance wise, I could feel a difference. I just hated the non resonated X-pipe I put in one of my setups. It was cheap, more like a hollowed out catyltic converter shell. You want something that is a true crossover or slight merge of a shared wall, that will help scavenge the opposing bank and you don't need a big cavity to do that. The borla accomplishes that well. You get acoustical harmonization, performance of an X pipe that the M54 really does responds to, and a free flowing high quality muffler. Its going to outlast a comparible magnaflow and sound better in my opinion. It's going to have a fairly aggressive sound, but less so than the magnaflow.

Okay, so on to the rear mufflers. I've tried magnaflow round race mufflers. They were long 4inch bodies. Close to 20 inches at least. They sounded awesome and are better up to task. The Aero's I'm running now are bullet proof, will last damn near forever, are great at attenuating some tone, but aren't optimal for a rear muffler replacement. They are aggressive and sound awesome, but drone as a rear muffler. They are better suited perhaps placed before the borla middle muffler. That's what their application has been with the M3 and others has been. Going back to the middle section, after I cut out the crappy x-pipe, I placed two glass packs in its place. In my case it worked well at taming it down a notch and killing some drone. That might be something to keep in mind if you need to take it down a notch. The aeros are perfect for that.

So that brings you up to speed on where I'm at.
I'm building a complety new exhaust for sections two and three. All 304 stainless. Exhaust is one of those areas that is very subjective and ultimately comes down to what you want. It's a compromise. However, there are new mufflers out there that let you have your cake and eat it. Aggressive, raw, fire breathing beast one second, and at the push of a button, --- quiet, civil, and tamed. Not oem corked, but tame. I'm building a valvetronic exhaust that has both the rear sections adjustable and middle section so you can dial in how you want it at any moment. Mufflers are on the way. I've sourced them directly from the manufacturers over seas that makes the ultra high end kits you see out there. It's probably going to be September before its done. I'm working on another secret project at the moment. I tried to upload some photos, but need to make them smaller. Anyways, get back to me. If you want to be a genie pig and put the borla in, I'd love to hear it.

__________________
2005 X5 3.0, 6MT, Alpine White on Truffle Brown, Sport, Preim, and Cold Weather, Alpina Stainless Headers, AFe Intake, UUC SSK, OEM 87's, 3.64 Differential Swap,Performance Modified Euro 2 Tune, UUC LTW Flywheel and HD clutch, Bilstein B12 Suspension kit
Future mods ZHP/Schrick Cam Shaft upgrade, Operation code name:Doppelschrauben-Kompressor

Wife's Ride: 2011 e70 X5 351 M///Sport.

Also in the fold: 2004 X3 3.0, 6MT, Black Sapphire on Terracotta, port, Premium, Cold Weather.