A few comments in response to the above posts ...
I owned a VAC Renaissance 70/70 Mk. III stereo amp and have owned continuously in my main system for the past six years VAC Renaissance 140/140 Mk. III monoblocks. Even the stereo 70/70 is a very powerful amp that can drive 2 Ohm loads (it is totally dual mono, all the way down to separate power cords and on/off buttons), and all Renaissance amps have very high quality output transformers and beefy power supplies, which are the two things needed for high current delivery. That said, I respectfully beg to differ from the above post on one crucial issue: while the Renaissance amps do have a variable feedback control, if you have to use it, then buy a different amp. Triode amps don't sound right when run with feedback (or more accurately, they sound like just another amp when run with feedback).
As for the PrimaLuna, not even their monoblocks will work properly with WattPuppies because, at 37 lb. per chassis, they do not have anywhere near the kind of output transformers and power supplies required to drive low impedences properly. VAC's Renaissance amps weigh 135 lbs. each and CAT's amps weigh 192 lbs. each for a reason -- very heavy-duty, high-quality output transformers and lots of power supply capacitance. With the possible exception of Antique Sound Labs, all of these cheap Chinese tube amps are indeed too good to be true.
With speakers that need a lot of current like WattPuppies, it is possible to do solid-state amps on the relative cheap and still get good sound and proper bass control. With tube amps, however, there is no way around spending a lot of money because the output trannies and power supplies needed to do the job are extremely expensive (for example, the 70/70 cost $14,000 ten years ago and the CAT stereo amp costs about the same).
Will a given tube amp work on a given pair of hard-to-drive speakers? If it takes two people to pick it up and it costs as much as a new Honda Accord, the answer is yes.