I have a UDA-1 and a modded (SDR) HD800. I don't agree with your assessment as I think the HD800 sounds fine with this combo, but not as good as I have heard the HD800 with say a my Liquid Carbon or my BottleHead crack. The differences are subtle, but better. If you can, you might look into mods for the HD800. The [COLOR=333333]SuperDupont Resonator[/COLOR] is easy and cheap. Read about it hear:
http://www.innerfidelity.com/content/sennheiser-hd-800-s-tweaked-and-delightfuland-french-diy-response
The UDA-1 is a very smooth DAC/Amp. In my opinion, too smooth. I'm hoping the Jodie as the amp and the UDA-1 as the DAC will breath some life in the HD800.
If the HD800 has too much treble for you with the UDA-1 then you should mod it, or sell it and get a warmer set of cans. Possible an HD600 or HD650 or maybe an Elear. You won't find too many DACs warmer/smoother than the UDA-1 to tame the treble peak.