I am not aware of any company that currently offers a simple, basic DAC with a decent volume control, and no headphone, and for my own use, did not want to use an outboard "volume pot in a case." Perhaps the SMSL S9 will fill that void. Apparently, audio component manufacturers do not currently think that such a component (without a headphone out included) is a big enough market to bother with. It will be interesting to see if the SMSL S9 - especially if it tests well here at ASR - can sell enough units to justify its existence.
Although I do not currently use headphones, I purchased a Topping DX7s from Drop for $370 earlier this year. I wanted a volume control plus balanced output to eliminate the need for a preamplifier. I find the DX7s is an excellent component, but the "not-yet released" SMSL S9 looks like it might be an even better solution for such a basic, simple audio component niche. (I couldn't find any listing of the S9 for sale via a Google search, but I think it is likely that the SMSL S9 will be released soon.)