Ron, I did try the Uni DAC... actually a demo unit that has one chassis instead of the usual separate power supply. It is the most "analog" sounding DAC I've ever heard. This has been said about the BADA 2 as well but it doesn't compare to the Uni in this regard. Very smooth, but very detailed as well. Hard to describe but it does sound like a high quality turntable. You'll have to take my thoughts on that with a grain of salt, though, as I don't have a lot of experience with vinyl. Ultimately I found it a bit too soft on the leading edge for my taste. It was a tough decision, but input flexibility and hi-res support factored into it as well. IIRC the Uni doesn't even do 24/96. But it doesn't really matter much because if you prefer the sound of the Uni to another DAC on 16/44.1 then 24/96 or probably even 24/176.4 or 24/192 is not going to push that other DAC ahead. I could easily be happy with the Uni as well.
Hans, I haven't had the regular Hiface, just the JKSPDIF. I am now using the Weiss INT203, which is more lively and open sounding than the JKSPDIF. If I had to choose between an interface upgrade and Series 2, I would probably start with the Series 2. It is not a subtle change. The interface upgrade would probably follow quickly, though, haha.
I actually downgraded my DAC to a Metrum Octave in an effort to scale back my system, but ended up with a highly modified MHDT Havana and it is the best one yet for me.
Power transformer replaced with an R-core, key resistors replaced with Shinkoh Tantalum, Vishay diodes, all Nichicons electrolytic caps replaced with Elna Silmic II, output coupling caps replaced with V-Cap Copper Teflon (<- this is the biggest upgrade!) as well as input caps and one more, other foil caps replaced with Auricap, WBT silver output RCAs, SPDIF RCA replaced with Vampire BNC. These changes transform the Havana into a new beast with the same heart and soul.