That combo can handle eight strings in its sleep. Some think there's an issue with the way the EQ is set up and suggest an EQ pedal to compensate - my ears are happy the way it is. And I'm not alone. Check all the bass vids on Face book. Find a player who can let rip and there'll be yellow in the background almost every time.
There is indeed an issue and it's not a complicated one: on the LM3 (and earlier ranges) the centre point on the high-mids EQ is 800Hz. There is then a MASSIVE GAP until the treble EQ centred at 10 kHz. But it's a point very easily dealt with by an EQ pedal if you want to give the usable treble around 3kHz to 5kHz a little boost, particularly if you are not keen on the high end roll off inherent in Markbass cabs.
Markbass have, themselves, dealt with this point in their new Marcus Miller range of heads with the high-mids centred at 1.4kHz and the treble centred at a much more usable 3.8 kHz.
Btw, I say this as paid up member of the Markbass club with no axe to grind here - my Markbass Combo (posted earlier in this thread) has been my goto gigging combo for several years now.