OK, I want to be able to use one cab at some jobs and two at others. I like 4-ohm's, either 1-cab @ 4 or two @ 8-ohms. Well I got a new cab and it's 4-ohm and if i want to add a 15 8-ohm to it I will end up at 2.7-ohm and will need a amp to handle that. So here it is, I know Carvins BX500 will run at 2-ohm and so will several Eden heads (not the new WTX500 though). I think Genz-Benz will update the Shuttle 6.0 for you. What other amp heads will go 2-ohm.