FWIW, the OBX exhaust, which is much cheaper, appears to be a "knock-off" of the AVO. I bought it (the OBX full exhaust, paid like $500 shipped) to mate up to my AVO DP years ago but haven't gotten around to it. Externally, it looks very similar (same bends, stainless steel, same size mufflers). Internally, who knows!? For example, the OBX downpipe looks identical to the AVO, even down to the bulge for the cat but, guess what, there is no cat in the OBX. lol I bet the mufflers have some horse hair or croutons stuffed inside!
Lastly, glad to see folks still look at my write-up. FWIW, the Grimmspeed also sells the proper 3" to 2.5" adapter (i.e., an adapter without the donut flange).