A 225/50-16 will maintain the stock rolling size, but you really won't see any benefit. The 6.5" wheel just isn't wide enough to make full use of the added width of the tire. The sidewalls will be pulled in, which means you'll end up with a contact patch that's no bigger than it would be with "correct" size 205s on there.
Either invest in some wider wheels ('98-01 2.5RS wheels were 16x7"), or just stick with the stock tire size.
Pat Olsen
'97 Legacy 2.5GT sedan