Mmmmmmmmmmm, that does seem a lot of dollar/effort to get to 185.
Are you looking to spend about 3k then? What kind of power you hoping for with the turbo?
How about buying a rear ended S3 & nick the whole front off it?? You'd have everthing then - Lump, downpipe, plumbing, uprated brakes etc, etc.
Could have a Golf S3 but without the downside of the weight of the 4WD system??