It really depends on what you want to spend, how portable you want it to be and what headphones you intend to get.
You can either go for a dac/amp combo, or keep them as separate devices. I personally tend to like the second option because its more versatile that way and most combos have seemed to me like a bit of a compromise. But that's not to say there aren't some very good combos out there.
As far as specific recommendations, there are so many good amps and dacs out there it is a bit hard to know where to start. If I was looking for a decent DAC and amp setup I'd look at something along these lines:
A Schiit Lyr and a Bifrost would be a nice option that isn't expensive, should sound pretty good and will run probably any headphone you should care to throw at it.
A Meier Audio Corda Classic and a Stage DAC would be another great combination, a bit more expensive, a bit higher end.
If you didn't want to spend much: A Musical Fidelity V-DAC and a Matrix M-Stage would be a very nice sounding budget option. Probably not optimal for driving higher end orthodynamics like the HE-6 or LCD-2 though, but most other headphones should be fine.
This is just scratching the surface really. Probably best look around at what experienced people say synergises well with whatever headphones you intend to get.