The HKS is cool, but definitely not silent. Not sure if there is wagon fitment. The nice exhausts that fit well, fit wagons, and sound awesome are all the pricier ones. I had GReddy EVO2s on my old wagon. Loud but sounded great and looked awesome. My favorite is the Stromung, which I have on both my Legacys. Very hard to find, but worth the search. Clean sound and much quieter than anything I've had. My wagon came with Ividia exhaust, which I wasn't a huge fan of, although I like a lot of other Invidia parts. You may want to check out Japanparts.com if you're up for spending big bucks on a JDM cat-back, but the tips won't stick out far enough for USDM bumpers.
The vette looks hawt. You should bring it on a canyon run!