Rich enough to retire today would mean between 2 - 5 million, 10 at the outside, I'd guess. Given your description of the limitations, anyway.
Sad to say that good as the MS3 is, there are compromises made to make it what it is that I'm not a big fan of. Some of them can be fixed, some of them can't. I can rework the shifter bushings and motor mounts, but I can't really change that's a cable shifter, and the slight vagueness that lends to the driving experience is something I won't be able to get rid of. It's always going to be FWD, which means grip limited at launch and no power oversteer. You can only fit so much tire under the wheel wells before having to roll 'em. For what I paid I couldn't ask for more, but if I was rich, I'd have been able (and more than willing) to spend more to get exactly what I want in a car.
That in mind, I'd probably buy 3 or 4 cars. I might keep the MS3 as a "beater" for the fuel economy/affordability of general maintenance, but that depends on availability of cars. I'm in Canada, too, and I'd like something that handles winter very well (not that the MS3 doesn't, but traction from a stop is nice sometimes).
Here is what I'd have in my garage.
- AWD utility vehicle, which means performance wagon. Probably an S4 or S6 Avant, possibly the RS variant if it ever makes it out here. A wagon is as much utility as I need. If I can fit skis, golf clubs, or lots of luggage for me and the woman, I'm happy.
- AWD toy car to tweak and toy with, which means probably the Evo X MR, the only Evo that is street legal in Canada. Maybe an older STI, because that 6-speed is bullet proof and I'm going to turn it into a 500 hp monster which the MR tranny hasn't shown it can handle yet.
- A Porsche because I want a porsche. Cayman S? Carrera 4S? Maybe a Targa? Who knows.
- A GT-R if I can get one.
I figure I could get most of what I want for about $300,000 to $400,000 if I do at least a bit of used car shopping. I could drop one or two from the list, deal without the Porsche and the Evo/STI, maybe. Depends on how much coin I have.
I'd also get a bike. Probably a 600RR.