The LTE slip on(which i run on my xmr), which in my opinion actually sounds better than the full duels(I've heard both), the duels are louder, but the slip on is deeper sounding).
And just to throw this out there if ya dont know, you wont need a tuner, and o2 bung sensors, and all that other stuff that comes with a tuner with just the slip on. Some people suggest it but its not necessary at all unless your running full system with the duels.
LTE sounds great and is very loud and very deep, deeper and louder and in my opinion better quality than HMF.. plus EVERYONE has HMF.
Another deep sounding one thats loud and has its own distinctive sound that is good quality is Ron Woods. Muzzy is similar to HMF for sound but a little better quality than HMF, and again not EVERYONE has it.
I like to be somewhat different than everyone else. To me, and where i ride, and who with, HMF is all you see. Nothing against HMF, I just think as far as exhausts, and exhaust systems go, Ron Woods, Muzzy, and LTE are better than HMF.
I see so many bikes with HMF exhausts that it wouldn't surprise me if they came stock on can am's in years to come. I think(and this is just my opinion maybe) everyone has HMF because they for the most part, really good sounding, and are the cheapest out of every kind of exhaust I've mentioned.