The subject car is '09 R3. I've read quite a number of exhaust threads with interest, but not seen quite the combination I’m looking for.
Edit:
Currently have stock manifold and BHR resonated midpipe into stock muffler. Looking for better flow and sound as below.

Objectives:
- Retain dual outlets & stock look
- No cat
- as smooth flow as possible
- maximum heat retention (reduce underhood & undercar temps)
- quiet as possible given the above constraints, minimum rasp
- modest cost, i.e. $1k or so total

I found the Porter 'steelpack' mufflers and had been hoping they would muffle well and not melt. However painmon.soror’s information that the glasspack removed the bass, and left the rasp, shot down that plan.

The current material list
- Maxim Works header
- 4 Moroso SS spiral flow mufflers. I think 2 will fit in the 'midpipe' area and one more for each outlet
- 3” SS tubing throughout
- 3" tips, I understand larger tips act like a megaphone
- All Swaintech ceramic coated

I'll tune the car with Mazdaedit when complete.

The full RB system is an easy option, but it is expensive, heavy, and I'm not a huge fan of the sound based on previous experience.

Feedback please!

 

I'm no expert by any means, but going de-cat will be loud, very loud. Resonated BHR race pipe is as I understand the best choice as far as not being as loud, raspy or otherwise annoying as others.
I have a Turbo XS installed in mine (race pipe and cat back), and it's extremely loud, not that I don't like it, but I have to granny shift at night to prevent from being pulled over in the city. I bough a Dynatech Auger-Style insert from Summit that I'll be installing soon (thanks to Painmon's posts) as to lower the noise level. I'll let you know how it is as I believe is the best alternative for our 8's when De-Cat.
Make sure you properly account for the ceramic coating, as that will run you about $40/foot, so that could be almost 1/2 of your budget if done correctly/professionally.

 

I'm planning to use the Moroso as it's an auger-style, but large diameter around the auger to aid exhaust flow. Lots of them since they are cheap and more (should) = quieter.

The header is at Swaintech now, I'm curious how much it'll be. A header/down pipe last year on another car was shockingly cheap, something like $75.

 

So, you are planning to run 4 total auger mufflers? You might want to consider using packed mufflers all the way at the end of the system where the exhaust is cool enough to not hurt them. Auger mufflers use destructive wave inference to reduce noise. This ends up targeting specific frequencies and all your mufflers are the same length (ergo the same targeted frequency).

Burns Stainless mufflers can be ordered with high temp stainless scrubble packing and can be rebuilt. In addition, I have had great results with Vibrant's mufflers in very high heat/noise scenarios without failure (Honda Accord race car that only had one small muffler doing a lot of work). Even a Magnaflow or Flowmaster muffler will be fine as long as it is behind the axle.

I am just worried that with 4 of the same style muffler, you will get some really strange resonant sounds.