Looks Like I just saw a new 5 ch. amp on the CT Sounds Site as I was browsing today. Looks like the Sub Ch is 1 ohm stable to 400 watts. Might be a nice Little amp for someone not wanting a massive powered amplifier. Thought Id share.
CT-800.5D // 1000 Watts RMS 5-Channel Car Audio Amplifier
The CT Sounds CT-800.5D is a compact full-range class d 5-channel car amplifier. The 5-ch car audio amplifier features a Low Pass Filter (LPF), High Pass Filter (HPF), and Bass Boost so you can get the exact sound you want out of your amplifier.