Hi Juanin, I know these are old posts but just FYI but Trelja comments are pretty funny really. It's obvious he's never heard these amps before or he wouldn't have this opinion, as far as the JD3000a being compared to the other brands listed that can easily out preform them all regardless of price especially the Airtight 211 making them sound down right uninvolving by comparison[I've hear these amps with Maggie 20.1's and against Joule, Wavestream Airtight]
The only exception being VAC only because they have the same type of realistic, live,warm sound all though the Jolida monoblocks have some real low end grunt and control that I haven't heard in a lot of tube amps. I've owned a pair of these modified amps for about 3 years now I don't see any reason to change them, great amps that sound great with a wide variety of tube preamps, Cary SLP-05 deHaviland Mercury VAC renaissance Viva Linea and my own SF-L2 preamp. An almost SET with lots of of bottom end, they can drive the big Soundlabs and Maggie 20.1 with ease but still sound great with more efficiant as well. I've seen them here for under $3,000 a pair used making them a total steal land of big buck tube monoblocks. These are great amps that are fairly inexpensive to retube but you can always got for the cryo RCA, GE-VT4C for an even more amazing sound! The JD3000b is a nice sounding preamp also for the money. As far as being reliable the only problem I had with one amp wise my own fault, trying out an untested GE-VT4C circa 1945 that blew an internal fuse. The amp was sent to Jolida in Maryland for repair which did take a while but the amp has work perfect ever since.
If you ever need sweet sounding amps with big time guts and control
over electrostatic or planar speakers these amps are it!
Enjoy,
Vinyl9