The downside of going to 17's, is that the ride will suffer compared to the stock 15's. Not so good if your car is a daily driver.
On a recent Vic MR2 Club run I checked the tyres on three different SW20's that were still running stock 15" wheels. When I asked the owners opinion about the tyres they were running they claimed not to have any problems.
One had Hankook K105's F/R
One had Falken 912's F/R,
One had Toyo T1R's F/R
I did note that they were all running the same brand front and rear, and although they all had 225/50R15 on the rear, I think at least one had a 205/50R15 front rather than the stock 195/55R15.
On recent checking I believe all those tyres are still available.