wheels & tires

i'm ready to purchase new tires and aftermarket wheels like the BBS LM's for my '84 911 Carrera but am having a very hard time getting good information from any of my local tire/wheel dealers. i want at least 17's and possibly 18's if they will fit even w/spacers. has anyone upgraded to 17" or 18" wheels from stock 16's and what tire sizes did you choose? i am looking for high performance, all season tires. thanks.

------------------