Wow, Syracuse, now thats alot of snow. I am often in the area and know the weather patterns well, I commend you for not having an SUV in the garage for that type of snow!
Lets talk about leases for a sec to give you some details. So its another form of financing first and foremost, so you have to know the formulas and you can determine if you are getting an OK deal. Usually dealers will give you the rates and the money factors so you can work to determine the math and how it works out. Just like with anything, you can work out a deal that meets your needs and its usually competitive with a finance. Residuals are what companies use to project the future value and determine how much the car would be worth book value wise when the lease is through.
Now others may come and chime in and argue other points, but trust me, ive done this for years and know the numbers inside and out, leases or no more or no less risky and have no other hidden costs. They are for those that like new cars every few years, you pay a little more over the years but you get much for for your dollars.
Now about the cars, as you can tell, I really like the F30, and may be moving to one in the future so it gets props from me of course as I think its going to be a great car. I think the N55 will be tunable for sure. As for the A6, im sure its a great car, but like you I just have a feel for how BMWs drive, though Im sure the S4 is a blast too. But if you like audi now, I think the A6 looks great.
On the 6er, as you noted, its a great car, effortless power, heavy, but you never feel it unless you track the car. The coupe is even better, imho and several hundred pounds less. If you were to get one, Id say go for the coupe, they are beautiful inside and out and ive enjoyed very moment of ownership...but it comes at a cost, a premium for sure, but the car is great period.
If you really are going to keep 2 cars, you have more options for sure, Ive just never been one to have multi cars, id feel heartbroken to not be able to drive the M6 all winter, and yours starts in september and goes to may!!! lol!
As for the M6, what can you say, its the best car in the world, imho. Its probably the nicest car I'll ever own unless I hit it real big! I got it several years ago when I had a different life as well, but things have changed and I have different responsibilities now, so I wont be getting the next M6. Mostly because I dont like the direction M took with the engine, and in reality, the car is going to be way rediculous in terms of cost, just based on what BMW did with the new 650i pricing which is about $20K more in MSPR when optioned out like my former '05 645ci, which leads to the reality that the new M6 will most likely be about $20K more as well from my '08 M6 (113K), which means that the new M6 is probably going to list for about $130K+ fully optioned
They will be an even rarer breed than my beloved beast! No, my next car wont be and M, but my next M will probably be the F30 M3
