David,
Teajay does concur that the 2A3 amp does not seem to have enough juice for the Ulf. For some reason the imaging of the speaker was not conveyed correctly with the flea powered amp. It just bunched up between the speakers. When I heard it originally I thought there was something wrong with speaker's imaging abilities. With Aric Kt-88 amp the imaging was much better but the midrange wasn't quite as luscious with the Triode 2a3. It would be interesting to try a 211 amp with the Ulf or one of the Line Magnetic behemoth 219's. I still love the midrange of the 2A3 so I think that the DI SE would be my choice but the regular DI is darn good also for 3k! Ridiculously good for the money!
I like romantic symphony music and Jazz and use old Beveridge Model 2 electrostatic speakers. I mention this just so you can know my bias in listening.
My wife is a professional singer so getting the midrange is key for me. I typically hate most rooms at the HIFI shows because they play HIFI over music. The DI and up the line can play music.
I want to give a plug for Mike at Audio Archon who is as true of an audiophile as you ever will meet. You definitely are in good hands with him. He has great ears as an even better guy.