Sounds cheaper to go the route you're planning to go.
If you do switch tires, I'd get something like this:
Tire Details - Discount Tire Direct
~Lots of modded Jeeps, trucks, and cars~
My favorite quote from the press release.. sad but true: "Chrysler claims its products, especially the Jeeps, can handle all sorts of terrible conditions, churning through muddy swamps, climbing mountains, and crossing rivers. Turns out they cannot even handle a car wash."