Adding a tube amp is a good idea?

Fantastic, thanks @ghdprentice 

My first better end system, 30 years ago, started with a Cary entry level tube amp (and a B&K digital HT preamp in front of it).  That started me down a long road.  

I am not familiar with that ARC amp you listed, but my next upgrade from the little Cary amp was a pair of ARC VTM 120s.  Those babies sounded fantastic, even with that particular preamp of dubious audiophile quality.  They could whisper sweet and quiet or they could scream.   And if it wasn't for how unreliable they could be when I flipped the switches on them, I'd still own them today.  

Variety is the spice of life!

Adding a tube amp in a second system alongside whatever it is you have now is a very smart way to test the waters.

If you are going to try a tube amp, Audio Research is as good a choice as any.

Not a huge tube amp fan here in that I listen to all genres and my favorite speakers in-house currently are not inherently tube amp friendly but have owned AudioResearch and am a fan.

Matching gear properly is especially important with tube gear due to higher output impedances that are typically found.

After many receivers, integrateds, separate solid state amps/preamp, hybrid amp, and a better solid state amp with a tube preamp, then full tubes for many years, I settled on a tube/SS hybrid bi-amp setup with a tube preamp, and tube monoblocks on the midbass/tweeters, and active low pass crossover to a SS integrated amp below 80hz to the woofers. The tube front end with tubes on the whole vocal range yields some pretty incredible results. It’s personal, it’s subjective, it’s system dependent, but it’s been delivering some amazing audio moments on a regular basis.

Most affordable tube amps don’t have great bass slam, extension, and control (actually many of the more expensive ones aren’t great at that either). A modest SS state amp used in the lower ranges delivers pretty well, where tubes tend not to.