Tubes with Infinity IRS Betas

The IRS line was um, problematic. The crossovers were designed empirically through trial and error, amplifiers be damned. Here's the measurements from Stereophile:

https://www.stereophile.com/content/infinity-irs-beta-loudspeaker-measurements

It's not so much the power as the wavering impedance curve with a low of 1 Ohm, far lower than most tube amps recommend, and the wavering  interacts poorly with tube amps, in the sense you won't hear a flat response anymore.

I might suggest you see if anyone has produced a better crossover for these speakers. If so, I bet they fixed the impedance issues. Otherwise, stick to beefy SS.

One tube amp designed specifically for problematic low impedance loudspeakers is the Music Reference RM-200. It even has a 1 ohm tap! 100w/ch from a pair of KT-88 or 6550 tubes/ch.

I recommend a new set of x-overs from dstechlabs.com (Fort Lauderdale, FL). 

SS amps like the big Threshold Class A mono’s with preferably ARC tube mono’s driving the mid/high panels is a well worn path. I recall Arnie Nudell voiced the IRS speakers with ARC tubes up top. The key is you need powerful ss amps to drive the bass towers, and reasonably powerful tube mono’s to drive the mid/high panels. Basically the more power, the better.