There are well respected amplifiers that don't double. Ayre, for example.
Ayre doesn't give a 2 Ohm spec but not sure why you wrote this. Ayre specs *all* of their amps as doubling into 4 Ohms. The AX-5 JA measured did show signs of stress at 2 Ohms but otherwise reacted well as the current demand increased on his test bench. I have the Twenty version of the AX-5 which is said to have slightly improved power over the original version and I will attest that it sounds really effing good driving my CS2.4SEs :)