For those of you wondering about aftermarket tire sizes and wheels. I looked some up on tirerack and there are quite a few choices for summer tires and a few all season options too for 20' wheels. They are almost identical in diameter to the stock 21" tires. Depending on wheel setup, you should be able to knock of 11-12 lbs per corner over the 21" arachnids. 45ish lbs of unsprung weight.
265/40/20 fronts
295/35/20 rears
Pirelli Cinturato P7 all seasons
Michelin Pilot Sport all season 4's
Michelin Pilot Sport 4s summer tires
TS Sportlines will be the cheapest wheels with tires when they come out, but they are still flow forged and heavy.
Martian wheels will be the best bang for you buck and they are light and forged. The M3P guys seem to like them. There aren't too many styles and I'm not sure when they come out.
Signature wheels are probably the highest quality, forged, light and perfect offset, but they are pricier.
HRE and TSW also have some nice wheels in 9.5” and 10.5”.
Also, great ‘performance’ all season tires at a good price are the Continental ExtremeContact DWS. Have exact 19” sizes but only 245-40-20 and 275-35-20.