I'm in the same situation, and after doing some research, here's what I found.
You can change your tire size, I've heard of some people going to 285/75R16s on the stock X rims. Personally, I wouldn't take it that far, that can lead to problems out on the trail, with too much sidewall, etc.
I'm getting ready to change my 225s out for 265/75R16s. But always check with the tire manufacturer for recommended rim widths.
A good, a.k.a. caring and competent, tire shop should be able to point you in the right direction as well.
Check out different tire manufacturers and tire sites online, one in particular will also point you to 'Recommended Installers'.
As a side note, the stock tires do appear pretty wimpy, but check out this vid
Not bad, all things considered, kind of warms the heart.