With two mini48 cabs and two mini 15's my suggestion would be two simple heads. I use a Markbass F500 with my Ashdown mini48 & a vintage and ultra rare GK115LB cab. However, as correctly explained earlier you'd be down to 2 ohms, so, send a more 'trebly' sound thru one head (amp) to the pair of mini48's, then line out to another head - eg F500 and feed that output to the mini15's (best sited on bottom). Thereby you can tweak tone for 15's making them bass heavier. It is almost a biamp set-up of sorts! And akin, to Alembic F-1X or Alembic Series Bass stereo output... Perhaps it should be asked: do you need 4 cabs?, albeit ultra compact! Alternative definitely worth very serious consideration: MarkBass NY604 - astonishing capability way beyond the laws of physicals and expectations esp evident with a throbbing, fat jazz bass sound!!