I think all 4 of my wheels are done...

Yeah, I was wondering where you got 18x8's lol.

If you can find a staggered setup, go with them. If you're staying with Mach 1's, last I knew, they didn't make them in 18x10. Staggered looks better and gives you a bit of extra traction... But of course, there's nothing wrong with having 18x9 all around. Don't go with a wider tire out back, unless you stay at the same profile. A lot of people try to put 275/40 out back and 255/45 up front, and the tire size difference is quite noticeable. Not only that, you really don't make it any wider. Not enough to notice.