If you're going to change wheels to 17" then have a look at the BFG AT in 275/65/R17. I have these on my GXL and find them great. They're a bit wider than the standard 265's on the GXL and give a modest height increase of about 12mm if I remember correctly. Not to much higher to effect gearing and they look great. Spare tyre cover still fits on too.
Cheers, Sam.