[BetaWolf]

I own an Atom stack and that's pretty much it. I'd like something higher end to power my HD660S, as well as give me more upgrade options. I'd prefer an all-in-one unit like Jotunheim. I'd like a neutral sound signature and better separation and detail than my Atom stack. Any suggestion or ideas are welcome.

 

[Mightygrey]

CMA400i is a nice all in one unit with balanced headphone facilities.

 

[m-i-c-k-e-y]

Consider a Audio-gd D-28 (review here) or a Topping DX7 Pro (review here and here). Matrix Mini-i Pro 3 is in your budget (review here). Fairly neutral, many connections, but not that powerful amp as the Audio-gd.

If you want a bang for the buck AIO check out Audio-gd's R11 R2R DAC (warm organic sound) and NFB 11.38 (neutral). All have powerful SE amp sections.