What wheels are you running now and what are you looking for in new wheels? Roadholding confidence, comfort, or both? I had staggered 16" Alpinas on my E9 and found it compromised the ride way more than I thought acceptable because of less rubber to cushion blows and the increased unsprung weight. The Alpinas including tyres weighed about twice the standard 14" wheel of the CS, which are actually very nice and light wheels. The Alpinas also made acceleration noticeably slower. I am afraid 17" will be even worse - but it depends on what you're used to and want.
Because good 14" tyres are difficult to find and I do like a spirited drive, my best compromise was 15" BBS wheels - 8J at the back, 7J at the front.
Even when rolled, 8J at the front is very likely to hit the fender, especially when hitting a bump into a corner. Also, having tried and seen about all wheel combos possible on a CS, I believe 7J is the largest you should fit at the front because more just doesn't look right.
