I owned a Wrx, RB5 WR sport with the Prodrive suspension, and a modified P1, as standard they are nothing special (p1 was), and are chalk and cheese compared to the S3. My brother now has a modified P1 and leaves my S3, but as they are getting on a bit and have been hammered, they are more costly to maintain and run a daily basis. His clutch failed in the first few weeks, and I suspect that now the suspension needs refreshing an updating all round. The Rb5 looked good, and needed the usual full decat, fuel pump, remap, plus a strict diet of Optimax. Fun to drive, but I'm too old for one now, and could not face the running costs my brother now has, we both find it hard not to modify cars, and hard not to drive them hard, if you can leave a car standard and buy a knock link, don't drive it daily, and can afford the rebuild then go for it. After being there and done it, I'd never go back. But if you've not owned one before, and have some spare cash, do it
I was tempted for a fouth, but would only buy a Jap Sti Ver 5 or 6 with a 'rebuilt' engine, the jap cars over the UK cars, have lighter panels, better turbos, better IC (Sti), alloy wishbones, different spec cams. I don't think a std Rb5 220bhp would have much over a S3 tbh. If you are interested get on rb5woc web site