Another rim size question

[revat619]

ok, here's the thing...I'm thinking about buying some new rims for my car and i know its been said that 18s will kill you on the performance side (rotational mass...blah, blah, blah...)Anyway, i think im gonna go with 17s, but im into the look of my car too, so are 17s gonna fill the fender gap with eibach pro kit springs? Also, what width and offsetts should i go with...i hear a bunch of combinations going around....17x8 front/17x9 rear....17x7.5 front/17x8.5 rear (also x7 front/x8 rear) and then 17x8 all around....and then there's offset which is pretty vague "somewhere between the high +20s and nothing above +40"....theres a heck of alot of offsets between those numbers. I dont know...somebody help please! Thanks.

p.s. i dont want tires with tiny sidewall either....sorry, i dont mean to be difficult <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=''>