[jphughan]

If you get a supercharger, you should factor in the cost of larger wheels and tires given that the car in stock form can break traction at WOT in 1st and even up through 2nd. Apparently it's possible to fit 18x10" wheels with 275/35/18 tires all around with no rubbing. You may be able to go even larger in the rear without issues or modification, not sure. Not sure what the maximum sizes are for 19" wheels since my research revolved around a potential track setup. And depending on how you drive, that extra grip from the larger tires can heat your brakes up faster, so you might need upgrades there too. The true cost of a supercharger is way more than the kit + installation.

But yes, I agree with the above poster that a supercharger seems like an awfully expensive proposition for a red light racer, and I too would recommend waiting until you're past the warranty period. And honestly, most people who track realize quickly that straight-line acceleration just isn't nearly as fun as ripping through corners, at which point you also realize that you can get much more fun for your dollar by paying for track days and buying mods that improve cornering and braking (square setup of wheels + tires, camber plates, upgraded brake pads or even BBK, etc) rather than staying on public roads and buying mods that add power. If you haven't attended track days a few times, allocate your fund to a few of those and thank/curse me later for getting you addicted to something awesome. As someone who DOES track, I'll tell you that power mods (even a tune) are the LAST thing on my list of priorities. I've upgraded brake fluid and pads, and next would be larger square tires and camber plates, then maybe a BBK possibly with dedicated track pads, and THEN power mods MAYBE. I'd supercharge only if you track frequently and have already done those other mods. Otherwise, these cars can reach license revocation speeds plenty fast stock, so unless you'll be driving somewhere where the extra pull at sustained high speeds can be used (or you just hate downshifting), I don't see the point.

Or just get the beater. I don't see a problem DDing the M3 -- sure the gas mileage sucks, but it'll take a while to recoup the cost of a beater on gas savings. That said, I too would cringe putting a dog in my car and such, and if your GF is getting tired of you using her SUV for stuff you consider too messy for your car (but apparently not for hers), I agree it's only fair to get your own car that you're comfortable using to support your lifestyle needs. And in any case, even if you're DDing the M3, hopefully DDing it up and down city streets and freeways isn't the ONLY thing you're doing with it (i.e. are you spending time on back road twisties and/or the track?)

But to each his own.