confused newbie - wheel sizes

[Big Red Cat]

Had my e85 2.0l a few weeks now & looking to change my 16" wheels to 17". I've just about got my head around offsets etc. & have been using the Rims & Tyres comparison site http://www.rimsntires.com/specs.jsp?item=Wheel- that I found from reading old posts on the forum. I've been browsing ebay & some sellers have a "check compatability" link to see if a wheel will fit - which seems very useful. However sometimes I've found that the dealer compatability has indicated the wheel is not compatible but if I use Rims & Tyres using the same dimensions they indicate the wheels are acceptable. How do I know which is correct?
Any advice very gratefully received.

 

[mr wilks]

Unless you really want 17's then i would skip & go onto 18's , with non runflat rubber the ride isn't too hard & the looks are greatly improved
On the offset caper ? you should be fine if sticking to numbers between 35 & 50 , the lower the number the more the wheel face moves towards the outside bodywork & consequently the higher the offset the more the wheel face moves in towards the discs .