MB heads run down to 4 ohm (so no 2 ohm operation)
The MB heads are very very good (thats why I use one), if you search for LMII or F1 you will find literally hundreds of posts extolling the virtues of both amps, there is a lot of love for these here. PLenty of other people have the less common heads too (TA501, TA503, R300, LMK etc). There are (as always) people who dont dig it, they tend to be very very keen on a more tube overdriven sound (major generalisation).
MB cabs certainly arent weak. They are voiced to work in a mix, and as a result some people dont favour their tone so much on their own.
IMO they sound fine - I prefer the sound of a Bergantino ae410 to the MB 410s (and staggeringly the Berg is cheaper in the UK) so thats what I went with.
As with many many others here I would strongly suggest trying the MB heads with other cabs too, but I wouldnt for one moment advocate entirely ignoring the MB cabs.