well...im running 4 x 10 and 1 x 15 with the PF-500 portaflex and im not too happy with the results. Plenty loud bot not much punch in the band mix, guitarist using mesa rectifier and drummer mic'd up to his own PA. I struggle to cut through but i think the problem is low quality cabs ( ashdown and bullfrog(?))
Anyhow i think the answer is to look at Bareface cabs, specifically the super twin 12. Ive read some pretty amazing reviews of their stuff, so it might be worth investigating?