It's going to be hard to find an aggressive tire(like you want) with 17s or 18s that will fit the KK. Stick to 16" rims. More sizes available, generally the tires are a little cheaper, and 16s are better for wheeling. You get more sidewall which will be better for airing down. I see you're in Westhampton, so I'm assuming you go on the beach.
Like I said, it's going to be hard to find aggressive tires in the size you'll need. Stock your stuck with tires around 245/70-16, or others with a similar height(about 29-29.5" tall). If you must get 17s or 18s, then stick to a 29-29.5" tall tire. Any larger and you'll need a lift or have some rubbing to deal with.
Did a little looking at the specs on Rockstars and the smallest size is 17x8, you might have some rubbing with stock sized tires because of the width. I'm not too sure there... either way, depending on the width of the tires, the 8" rim might be too wide.
2011 KK - Skyslider - JBA Adjust-A-Strut - OME 731 - Bilstein Shocks - JBA UCA- 245/75-16 Duratracs