20k for 20 more lb/ft of torque? I'm sure a 545 with a supercharger can easily overcome that difference.
If I had an ///M car, I'd drive it everyday. You buy cars to enjoy them. You live once. Enjoy them. I had an E55 AMG, enjoyed every minute I drove it.
Although I'm on the young side here (29), I have a great appreciation for life and the fact that you never know when it's your turn to go. If you can afford it, do it. It's only a car. My step-father used to flip cars every 6-8 months (wow, now I know where I get it from), not cheap cars either, they were all MB's that cost at least 80K. Most were AMG's too. Anyway, he worked for them and enojyed them. He also died of a massive heart attack at 52. Did he get to take any of it with him? No. Did he enjoy driving each and every one of those cars? You bet.
Sorry for the long reply. Life is just too damn short not to enjoy what you can when you can.
Now, go get and ///M out of the garage and drive like you stole it!