Hey guys.... 1st post on this forum. I need a little help and convincing about my upcoming car purchase. Here is my current car situation:

2011 Ford Taurus - Company car - daily driver
2008 M5 - Dinan S2 - was my daily until I got a new job about 6 months ago.... probably my favorite car (overall) that Ive ever had
2010 GT3 - weekend warrior.

OK... so my lease on my M5 is up at the end of summer. I am planning on getting the F10 M5 in its second or third year of production (2013 or 2014 model year) The residual on my M5 is waaay off so I dont think I am going to be able to get anything close to a good deal to buy it out at the end of the lease... so I am planning at this point to part ways with it. I want to mix it up for the next couple of years before I go back to the M5.

Here is what I was considering:
2011 550i - just too small for me.... if its not an M5, there is no way I would own something this small again.
2011 750i - awesome sedan - very big
2011 X5 50
2011 X5 M

SO, I think Ive decided that I want to give the X5 a shot for a while. I cant decide if the X5 M is worth the extra $$$. I am planning on ordering a X5 50 and getting it fully loaded. everything except for 3rd row seat. Nappa leather, everything. MSRP should be around $82k. X5 M as I spec it will come at about $99k. This car would be used for evenings, weekends, road trips, etc.

Here is the dilemma.... Im having trouble justifying the extra expense of the M. If this was a comparison between the former 4.8 engine and the M, I wouldnt hesitate. But the new turbo in the 50 is VERY good. 0-60 is claimed to be 5.3, but the X6 50 has seen 0-60 in 5.0, which alot of magazines are saying the X5 50 will likely hit too.

One other thing is that I need to tow. Not that often... maybe 5 times per year.... I track my GT3 and have been borrowing a friends truck to tow it so this is part of my reason for getting an X5. I know the M isnt "supposed" to tow, but Ive seen people do it anyways.

So, whats the opinion here? I know this is the X5 M forum but you all must admit that the new engine has made the X5 50 a great competitor.