about the best you can do is a 245... might be able to hit 255, but the chances are you'll rub. I can't tell you who makes what, but... these are your options:
245/55 R16 (very close to original height)
245/50 R16 (a little bit shorter, would help prevent rub)
255/50 R16 (very close to original height)
255/45 R16 (a little bit shorter, would help prevent rub)
You should have I believe 225's stock, so you're only moving up in section width a little less than 1 inch (1"=2.54cm), and due to your small wheel and taller sidewall that will not equate to 1" gain in tread width. Section width (the first three numbers) are a measurement of the width of the tire at the WIDEST POINT. Tires balloon out; the more sidewall you have, the more there is to balloon out. The key thing to remember is that for handling, width isn't your biggest factor to tight handling. It's sidewall flex and tread design that are the two most important factors. Having a shorter sidewall will result in improved steering response and better feel of the road.
Taking all of this into consideration... you need to ask yourself how long you intend on running the stock wheels and how soon you need new tires. If you're due new tires in short order and you would like some wider tires for a little enhanced grip (don't expect handling from this) then go ahead. But don't go with a cheaper tire so you can afford a wider section width. The tread pattern and compound is more important than the 1/2 you'll gain in actual tread width. If you've got some time before you need new tires, just run what you've got and save that extra change so you can replace your tires when they need it with new tires AND wheels; go with a 17" or 18" and throw on some 245's... THAT WILL make a noticeable difference. (if 17" is good enough, keep an eye on e-bay for factory 17" wheels in a set; should get them pretty cheap)
Good Luck!
