I was wondering if it would be possible to get a hold of some 18x14 inch wheels, and what would the tire size be? My 'x' is an 03 se sc

No tire that could fit those wheels would fit an Xterra in the first place.
Nothing wider than a 10" wheel belongs on an Xterra unless it is HIGHLY modified. Largest tire you can fit is something on the order of 35x12.50 and that's with the maximum lift plus some moderate sheet metal trimming.

Why in the hell would you want your X to look as stupid as it would with "wide" wheels?

im weird like that, i think about really stupid things i could do to a car for hours and since i have only seen a 14 inch wide wheel on a chopper bike, i wondered what itd look like on a truck or car. i really dont have the time, patience or money to do any of that though, im mainly after a wheel that is slightly wider than stock, and no more than 18x9, give or take an inch.