2 ohm head unit
 

Can anyone tell me if there is an aftermarket head unit with 2 ohm impedance?

My stock system is 2 ohm and will overheat a 4 ohm head unit in its current form. Before I knew I had a 2 ohm system, I installed a 4 ohm head unit; it overheated and the volume was very low compared to the stock head unit.

Can I wire a 4 ohm head unit to be compatible with a 2 ohm system (i.e. wire the front speakers in series, wire the rear speakers in series to get two 4-ohm channels)? Will this affect my volume still?