18" inch wheels will be larger and as a result be heavier and changer your gear ratio...it's not a downgrade...it is a tradeoff...you improve looks (with a TT traction...wider tire widths available) and you lose some performance. Your fine with the stock brakes...but your right they will be less effective with larger wheels. Do a search on the site for a brake kit using stock calipers but bigger rotors. Someone is selling that kit and I'm not sure who it is. Hope that helps...have a great Christmas!