What headphone amp to use with Sennheiser HD800?

A Ray Samuels B52 is a fine match-up. But realize that the 800s can be bright and clinical with some CDs with any amp.
I think tube amps are best for them.

A solid state amp such as the Burson does a good job with them.
Generally, with sennheiser line.

You should look at Head-fi.org for more info. I use a Bottlehead Crack with great result with my HD650. I know they are not 800 but its all i can afford. Anyway i have try some SS amps and for sheer musicality tubes are better. I havent tried the HA-160D but its a very good dac/amp from what people are saying. With SS my 650 sounded bright and digital, but when i tried the BH Crack, it was music like it meant to be.

So Far I have tried my HD800S with my Mal Valve on both the 8 ohm and 32ohm settings the 32 was much more balanced sounding, It sounded great somewhere half way between the Stax 007 and the LCD3. It sound very natural with a rich and prominent midrange, the treble is a little too much, not bad just a little much and the bass is all there but a little shy.

Now I'm listening to the HD800S with an original Krell KSA 5 fully recapped and upgraded, WOW they like current! They have no shortage of power with either amp both are far more power than the headphones could possibly take but both amps or the headphones rather sound a little congested when pushed hard on complex music and I know for a fact its not either of these very powerful amps. With the Krell they sound even more alive, transparency is about the same as the Mal Valve but the frquency balance is even better with the Krell, strong assertive fast bass and blends perfectly with the midrange and slightly more balance treble. I'm guessing the Schitt Audio Valhalla II will sound awesome with them. Right now I'm swapping some caps out in mine; with upgraded tubes it's an extremely impressive amp very close to the Mal Valve (with upgraded tubes that cost more than the amp lol). I think the Krell is the king relationship wise here, it just sound so right and musical and very punchy like live music and very close to the Mal Valve transparency although I think the tube amp has an edge there. The krell sounds limitless, it has absolute authority over the HD800S, the notes last forever, there is layers and layers of depth and complexity it just sounds lush and gorgeous. The micro and macro dynamics are as good as it gets with this combo.
All listening was done with the DCS Debussy playing fully uncompressed high bit rate files, the amps and Digital have separate power isolation transformers running off a dedicate 20amp line. Analysis Plus Solo Crystal cables were used throughout..

The Bass with the Krell KSA 5 is comandingly rich and wonderful. Deep, Powerful and controlled, bottomless and effortless. This headphone can do Bass with a powerful amp! I bet the Pass Labs and Valhalla II sound very close.