Is the 2A3 amp in your system right now? Or are you currently building it?
I've only heard the WL Ultrapth-bp preamp once while I was at MAF. I can't really comment on the UP-bp because that was also the first time I had heard the Oris horns. It's just impossible to comment on the electronics used in a system when you aren't familiar with the speakers. I can tell you that the entire package (Oris horns, DRD amps, TT and UP-bp) sounded pretty good.
I have recently bought the NOH preamp in kit form. How's it sound? great! Forget everything you've heard about passive amps when applying it to this Tx102 based preamp. This thing sounds great from low frequency to high...from high(ish) volume to whisper quiet. The music is just so darn clean and clear...but without any bass or dynamics missing at all. It's really a joy to own/listen to. You shouldn't have any problems with noise from the preamp either...I can't hear a lick of noise coming from my DIY edgarhorn speakers.
I'd love to hear an update on what you decide...keep me/us updated
and have fun!
(by the way...nice system)