I don't see where the silencer-shop-direct does anything for you that any dealer couldn't do.
Form 4s for a Trust/Corp can be submitted electronically by any Class 3 dealer. (ETA: yeah, you're right about the eform system being crippled. My point was they talk about it like it is something special, when it is not.)
Nice marketing strategy, but they aren't doing anything for free. ($270 for a $200 tax stamp -- they're including the transfer fee/etc)
Unless they have a great sale price AND their local contracted dealer has it in stock, you're not gaining a thing by going through them rather than straight through a dealer.