i had the previous version Nagra HD dac, with power supply and base, and the Lampi GG1.5 (which i owned) and Aqua Formula all together. there is a thread here someplace about it. i ended up preferring and buying the Formula, selling the GG 1.5 and sending the Nagra back.
then three months later i did hear a newer version of the Nagra HD in my system, and then i slightly preferred the Nagra HD to the Formula......although not enough to buy it.
in the background to these dac adventures i had been 'stalking' an MSB Select II for 2-3 prior years; hearing it's magic at shows and trying to find a less costly alternative. 30 days after my Nagra HD <-> Formula compare, i did buy an MSB Select II, which i have written extensively about. 3 years later i'm still thrilled with that decision and have not looked back. it's amazing.
the Nagra HD i heard in my system then is not close to the same realm as my Select II to my ears based on my experience. Ed (EuroDriver) from Taiko owned that Nagra, he could identify which exact unit that upgraded one i had was......i'm not exactly sure).
i think another thing to consider regarding the MSB and the Select II in particular is it's modular upgradability and what that modularity does for interface optimization. the MSB Pro USB interface is pretty amazing. i know there are third party alternatives to choose from, but the synergy of that type product is hard to beat.
i hope that helps.