You could either. My magna flow replaced the resonator in the middle and ran pipes off that. The Remus is connected from the left side...
Remus Axle Back Exhaust for 04-10 BMW 525i/530i E60/E61
My RD sport is quad mufflers, the right side muffler is on a angle to fit and is indented. I bought it from a member here who had modded it. I'll see if I have a picture. I'm not sure how much modification something like a RPI would cost to have the pipe run from left side muffler. There aren't really too many quad options out of the box without some custom work.
Umnitza sells a quad exhaust with everything, but I have no idea how it sounds. I know some other people on the forum have the exhaust. May be a good option for a good price that doesn't require a lot of modded stuff. The video sounds pretty good on a 530i.
E60 (5-series) Quad Exhaust [UMEXHAUSTE60] - $699.95 : Umnitza|BMW Angel Eyes|LED Angel Eyes|Headlights|Lighting|Performance|Service|87748 66489

 

I was checking out umnitza and i called them. Im just not to hot on the tips and they said there wasnt much room to change them. Plus I have not ran across a utube of a video of how they my sound yet

 

You can probably modify those pretty easy, you can cut them off and have new ones welded on, it obviously adds to the cost depending on what you want.

 

Hummm I wonder if I would be able to use the Borla 2 in 2 out or will I have to go to a 2 in 1 out

 

go with 2 in/2out - you can see in this thread

https://5series.net/forums/e60-parts...talled-135164/

 

Cool but r the pipes low? Is there good clearance? If other work needs to be done will the pipes have to be moved like a rear diff service ect....

 

What TexPhil said, you can cut them and modify or you can put sleeves on them.
Not sure who you spoke with on the phone, but that's pretty common, we offer straight cut pipes, most people like them, but some change them.

 

went with magnaflow..

 

Nice. Are you done installing it? How's the sound? I just ordered my Magnaflow catback from Magnaflow Exhaust|4WO, but I've read somewhere that this exhaust produce drone at low RPM. Did you experience this? I might also add resonators if this catback will be too loud.

 

No drone at all, its sound awesome for my taste, not to loud.
will get a sound clip later on.