Well, it's almost a certainty that you will NOT be going OEM. Too pricey.

I'm suprised that none of the muffler shops even recommended an aftermarket.

Basically any will work as long as the muffler shop can adapt to the existing pipes. The trade offs will be: sound, backpressure, longevity and price.

Many members have put on PowerVault products but the preference seems to be the PV1 which is no longer available.

My 2 cents worth of advice is to tell the muffler shop that you want to use what they have available & will fit. Minimize back pressure & go with Stainless Steel if you can afford it so it'll last longer.