Tubes with Infinity IRS Betas


I have always ran my mid/high panels on my Betas with a krell Fpb400cx. A friend let me borrow A pair of Primaluna Prolouge 6 Amps with Kit-120 tubes. They sound really nice but I am not sure if they are powerful enough for the Job. I have a line on a nice set of Vtl 300 deluxe mono blocks. I quess my question is what would I gain with the extra power. I listen at maybe moderate levels at best. 
rvito
I often wonder if they are worth the hassle and what would I replace them with. I would like to pick up the Vtl 300’s and give them a try but I have concerns there as well. I know they are long in the tooth and worry about reliability issues. I spoke with bea at Vtl and although pleasent to talk to the vibe I got was they really don’t care about past Products they would rather promote the new which I get but with a daughter in college my budget won’t allow it at this point.I love my Infinity speakers of which I have the Betas of course and the Gammas, Ren 90’s, Kappa 9. I cannot seem to find much information or opinions on the Vtl's. 
You said it yourself "many moons ago"...let’s say customer A has a nice used pair of Beta’s, a fully refurbed Threshold S/500 Series II (of which you’re very familiar) and a 2nd hand ARC Reference 110 with new NOS tubes, where are you going to put the tube amp?
Wouldn’t change anything, if fact back then our hearing was far more acute, still remain the same, as that downward sliding impedance curve
3ohm@150hz
2.5ohm@700hz
1.5ohm @3khz
1ohm@20khz
This would still knock the HF out of the tube amps, on the Threshold s/500 things will remain flat out to 20khz.
And the Ref110 should cope still with the bass tower impedance, it doesn’t go below 5ohms on the Stereophile graph.

Cheers George
I have had a set of IRS Betas for just over 10 years now, and still have my original pair of Quantum 5s. In the past I have also had Kappa 8s, Kappa 9s and IRS Delta's.To power them properly & safely, I personally have had good results with the older vintage Threshold amps, S300 MKII, S350e & S500e.I have also had good results with modified Halfer amps as well, some moderately modified stereo DH200 and DH220s, and more recently a pair of extensively modded mono Hafler DH200s with custom driver boards.With the Betas I like to use the modded mono Haflers on the mid-high towers and the Threshold S350e on the bass towers, and that setup has power to spare and is the best sounding combination so far.Last year I picked up a pair of Doge Audio tube mono amps, and they do a a nice job on the mid high towers in class A mode. They do run very hot though, definitely need to make room for them to breathe.For the Haflers, I usually do not push the idle current, so they run warm but are not outrageous power consumers.The only thing I regret is not having a big enough room to do the Betas justice.Even so when people hear them for the first time they are blown away.