I understand where you're coming from. I, too, had the desire to get myself an M5 ... so one day I drove my 550i to a BMW dealer and came home with a new M5. In a nutshell, an M5 is basically a show-off, look-at-me car. Sure it has 5 seats, but it has no financial practicality whatsoever ... gas every 2 days averaging 10-11 mpg, sky high monthly payments, big on insurance, pricey 10w-60 oil at $12/qt, new rear PS2s every 6k-7k, etc. But my best memory? The trumpet blare of the V10 at 8000 rpm through Dinan pipes ... major chills. Lived it, loved it. Would I do it again with the newer M5? No. My 335 is the best balance of practicality and performance without destroying the bank account the way the M5 did. I can't imagine how much worse that would be had I kept it past warranty having to pay crazy money for brakes, plugs, trans/diff fluid service, even SMG repair.
2011 E92 335i 6MT (Space Gray/Coral): M-Sport / Premium / Convenience / Navi / L7 / InvisiGuard / Dinan Exhaust & Pedals
2011 CR-Z EX 6MT, 2008 GSX-R600
RETIRED: 2008 Dinan M5 SMG, 2006 330i 6MT, 2006 Dinan 550i 6MT, 1992 Accord EX 5MT