Need help with offset

I plan on buying some c6 wheels for my 99 ws6 and was wondering if anyone could help me select a set of wheels that would look good on my car. I want 2 pick up a set of 18 inch c6 wheels. I would rather have a wider wheel in the back but thats where im clueless on what to look for. Im affraid that selecting the wrong offset will cause the wheel to sit in too far off the fender. I was also wondering if anyone knew a good company to order these wheels from or if anyone had any pics of c6 wheels on your Trans am. dont be affraid to post pics of them. Thanks and any info will be appreciated.

ok cool that helps me out. now i just need a site that sells these wheels.

thanks for the info. Rich

those wheels are nice but i think im looking into just the silver ones or the black ones.