Tube Monoblocks w/- balanced inputs?

You havent made clear if your friend is simply looking for balanced input connectors or true balanced/differential amplifier circuits.

Balanced circuit:
100wpc Manley Snappers

Balanced Inputs:

Manley Neo-Classic 250(wpc) monoblocks. Just out of range, but someone has a used pair listed here for $4,850.

Antique Sound Labs Hurricane DT Mark 2 (200wpc). There's one listed here for $3,900

Rogue Audio Zeus (225wpc). A bit out of your friend's range, but worth considering used at $4,900. Used M-150 or M-180's will likely be within his price range.

Rogue dealer here***

He should certainly take a look at the Rogue M-150's. They are right at his price point (the M-180' would also be a great choice but a tad over his budget).

Excellent amps!

Taylor
Goldprint Audio

Manley, BAT, VTL

Sonic Frontiers Power 3 tube monoblocs' circuits are fully balanced from input to output, as are their output transformers. I used them with 3.6's in a 27'x 16' room and they were a nice match. IMO: if possible, put the 3.6' on the long wall. Good hunting!