Listen to Ovekam, he knows his onions.
I would have suggested you test drive a 116i, then if you don't think it has enough for you, try a 118i.
A 6 mile commute isn't much so even though you won't have any DPF risk as in a Diesel (Saying that I do 2000 to 4000 miles a year yet still own one and have no DPF issues). The car will still benefit from at least a decent run on a monthly basis so it can have a bit of a blowout.