With a 2G B6, I'd probably go for the Busa shock and if you don't want the tail raised, lowering dogbones should keep it normal. They're usually pretty easy to find on ebay cheap - maybe even easier to find than a B12 unit.
If you do decide to go with a 2G B12 shock, try to find one from a naked version, they're stiffer than the "S" model shock