I am going through exactly that with my FX50 now. It sucks from a stock size 265/45-21 perspective. I think I might have found an option in the 275/45-21 size though for all season though.
The Y34s are great cars. They just came out a bit early to have any of the cool tech stuff though. I had almost no problems on mine, I think the only problem I ever had was that an ABS sensor go out over 6 years. Other than that it was just routine maintenance stuff. I have the two hairly mutts now so I had to get something bigger otherwise I would probably still have that car.