Why should you buy one? Because you want one, or any number of reasons.
Personally I wouldn't buy one, I looked at the MK200A or whatever their flagship head is. Awesome tone, but it only has one tone, if you want versatility look elsewhere. It is also far more expensive than it's competitors, a used one sells for about as much as a new SVT-CL.
I do not hear great things about their cabs at all, I personally haven't used them enough to compare them though.
Carvin LB76 / Dingwall ABZ ! Support Local !
MarkBass SD 800
Epifani UL2-310 / fEARful 1212/6
! Rocking against all gods !