Welcome squatch!
I have switched out my OEM Maniverter to a cheapo eBay header and a 2" exhaust system with two 29" Cherry bombs and a Cherry bomb turbo muffler on my 94 VX. It didn't lose me any mileage, but it didn't really help a whole bunch. I had to fight the urge to goose the throttle since it sounded so nice, lol.
I can totally agree on the aftermarket stuff being cheaper than the OEM stuff I did my header, cat and the rest of the system for $150 (welded up by a friend of mine) as apposed to the $200 from Honda just for the Cat Converter. Too bad that 2" exhaust components are cheaper than 1.75" ones
I wanted to stay nearest the stock sizing as I could to maintain exhaust velocity.