Nav or no Nav is becoming like Coupe or Roadster - it splits people down the middle

If you don't want it, you should be able to find yourself an even better bargain as cars without are worth less.
In person, I have only ever seen Piano Black trim in an M outside of the standard Carbon Leather, the other options are very rare so wouldn't worry too much.I think the Extended Leather option is more common than wood trim in an M, and I've never seen one with the alu dash.
There are two Stereo upgrades; 'Business' is the standard one, 'Hifi Speaker System' is the middle one and top spec is the 'DSP/ Carver' set up. Disappointingly none of them are mind blowing as BMW stereos never are, but you have that engine anyway
There are also three blacks. Black Sapphire is by far the most common, but Ruby Black (red tint) and Carbon Black (blue tint) were also available at extra cost and much rarer.
Most cars have a few options on them, there weren't many to choose from anyway and there are very few base spec Ms out there, so you will find most of them are similar. Heated Seats, Bluetooth, Cruise, Extended Leather, Stereo Upgrades, Parking Sensors, Cruise Control and of course Sat Nav are the main ones to look out for.
Make sure it has FSH with the 1200 mile running in service present and correct, refer to the buyers guide and you should be fine, there are loads for sale at the moment and they are giving them away at current values. Enjoy!