There's a fair amount of misunderstanding about tube amps and what distinguishes a good one from everything else. To drive speakers that feature low impedences in the bass, a tube amp's wattage rating is largely irrelevant - what matters is the quality of its output transformers, which convert voltage to current, and how stiff (robust) its power supplies are. Really good output transformers are extremely expensive and heavy, and stiff power supplies are very heavy. Thus, there's an old adage, which is generally quite true, that the heavier and more expensive a tube amp is, the better it's going to sound on hard-to-drive speakers. To put things in perspective, 100 watt/channel tube amps tend to weigh 50 lbs. to 80 lbs. What is generally recognized by knowledgeable audiophiles as the most "powerful" regular production tube amp, the CAT monoblocks, put out 100 or 200 watts/channel (depending upon the model), but weigh 192 lbs. per chassis and cost $30k to $50k (depending upon the model). In short, most tube amps, including those that the magazines have concluded are "good", really can't drive tough-to-drive speakers like Wilsons (or anything else that drops below 4 Ohms in the bass).
An amp that was well built and is available for very reasonable prices used is the Sonic Frontiers Power 2 (it features balanced inputs, but is single-ended). If you can go up to $3k or $4k, the BAT VK-75 SE is a good amp that is fully differential balanced. Also for $4K is the VAC 70/70 (Mk. III or Signature), which is an amp I have owned for ten years. It is a tremendous amp that does it all (fully point-to-point wired and fully Class A biased, zero feedback, directly heated triode 300B output tubes, auto-biasing, sentry circuit to automatically shut down out-of-spec tubes, and totally dual-mono all the way down to separate power cords and on/off switches - the amp will drive 1 Ohm loads), but it does not have balanced inputs - I run a balanced cable to it from my balanced preamp, and use Neutrik convertors on its single-ended inputs.
My advice is to stay away from tube amps for low impedance speakers unless you are prepared to spend what it takes to get one that can do the job. Unfortunately, most tube amps manufactured these days cannot.
Good luck.
