Thanks DDMan! Since Tirerack didn't list weights, I didn't consider that Bridgestone's site would, but they do.
The TS's 195/60/R15's are 18lbs. per the Bridgestone site, so:
WRX's 16+21 = TS's 19+18, it's a wash.
I was hoping the the WRX ones would weigh less than the TS ones, but at least they're not heavier, and they're wider.
I think the lugs are the same taper, but wanted to be sure. Looks to be the same.
People have reported both 53mm and 55mm offset on their stock WRX wheels, there were few threads about this when I searched. Seemed like it was related to mfg date, but no one ever came to a resolution on why, at least that I could find.
Anyway, thanks for the help.
Steve