I went back and forth on this one also so I understand your dilemma. I've dumped a lot of money into my ride so money wasn't really the concern for me, it was just the time and effort and the actual 'necessity' of it. I don't think it's a bad investment though. You should be able to get most of your money back for the mod, but it all depends on the buyer. I just decided not to cut up my car and rear seat setup and leave it as is and run my 275x19s. My car is now pretty low in the back and it has a great stance and I don't think i needed 315's to make it look 'slammed' or 'grounded' or whatever. Yes, it would probably look a little more potent with slightly wider tires in the back, but not enough for it to be a necessity for me. Yes, I'll probably lose a little off my 60-foot times, but oh well. My happiness with the car doesn't depend on 10ths of a second. Plus, if you get those mini-tubs and you swap in big back tires(315+), then you need to focus on widening the fronts also or else you'll end up with too much grip in the back and you'll have a push in the corners. A lot of people who put those really wide tires on the back now struggle to get the fronts wide enough to balance the car. I've got a cage over the rear now along with my battery, so with that extra weight along with some soft 275's I'm getting some decent grip and feel like I can manage without the 315's. I put some 265's up front and dropped a lot of weight off the front so with the nearly square tires and the extra weight in the back along with less weight in the front, I'm getting a good balance. But that's just my take on what I need my street ride to be. Everyone's different. If you're trying to be competitive in racing or are just trying to get the absolute most out of your car, do the mini-tubs and think about what you're going to do up front also if you'll need balance. Again, it's not a bad investment and you'd probably get your money back for it. Either way, good luck with your build!