I've gotta say, the 1350 is sensitive enough, the E5 seems to be more than enough amp for me. The output is buffered, so there is more than sufficient current. It's flat (there is a tad bit of bass roll off), has an incredibly low output impedance and really sounds great. Nwavguy tested it, and it performed better than the E6. It would seem that the early E5 had a CMOS based opamp. I took mine apart and it's definitely not CMOS based. It certainly outperforms any CMOY, and I really think it is all you need for the 1350.
Thanks for the info. I can get my hands on a CMOY to play with, and for the $20-$25 I'll probably just order an E5 to play with as well. I'll probably just drive myself nuts listening for differences (and not getting work done!)