I would suggest the coliseum 880 1x18" cab, with the Cerwin Vega. It is incredible how much top end they have for being an 18" and not being woofy, and the same for the Marshall 1x18 cabs with the Celestion G18Q-400. I run two of the Sunn 1x18 cabs with the matching Coliseum 880 head, which peaks at 880 watts at 2 ohms. On top of that I run two Marshall 1x18" cabs from the JCM 800 bass series, with a 400 watt Marshall integrated bass system head. its a killer rig and I would suggest either of these cabs, but it may be kinda hard to find one of the Coliseum cabs.
Joel