What are you looking for in an amp? I have not heard any extremely high powered tube amp that I would want. If I needed such extreme amounts of power, I would look at solid state. Most of the high powered tube amps have a "brittle" sound, to me, and are somewhat harsh sounding. High powered solid state sounds less harsh; the downside being a kind of lifeless and unengaging sound unless the volume is pumped up a bit.
I don't know of many speakers that I like that benefit from this kind of power. Most of the stuff I like can be reasonably powered with 40 watts or so, and there are 40-100 watt tube amps that sound pretty good.