Amplifier considerations, PrmaLuna EVO 400 versus ARC Reference 160 S. Is ARC worth it?

My Primaluna EVO Power amp has benefited greatly from using Sophia Electric blue "coke bottle" EL34 ST  A-matched tubes in the power tube positions. Strangely, Sophia's 12AU7 tubes are not compatible with PL amps - a fact they mention on their site.. For that matter, most of my vintage 12AU7 tubes do not play well with PL amps or preamps in the driver tube positions. However, PL's branded 12AU7 tube sound pretty good.

The 12AU7 gain tubes on both the pre and power PL amps can be rolled. On the power amp gain tube positions I am using vintage Amperex 12au7 Bugle Boys to great effect.

I am also using Mullard metal base GZ34's in the rectifier tube positions on the EVO 400 pre. These vintage tubes are, of course, pricey but worth it.

@ bolong: Sorry I missed your question. I started with one EVO 400. I used at first the stock tubes and ran the unit in stereo. It was really impressive, especially in the mids and lower highs. Vocal were lush, full, and natural. Nonetheless, the bass slam was not there. I then moved to KT-88, I liked the sound of that too, the bass became tighter and faster. However, the top end did not have the bite I liked. I then moved onto the KT-150 which suited my tastes the best, Tight, fast, clean, with a top and bottom end that had authority, However, I could tell that the grip on the bass response was not as iron clad as it could be. I then saved up and purchased a second EVO 400 and retubed it with another set of KT-150s. That is when the late night to early morning listening sessions started. The change is subtle, but what you get when you run them in mono is better damping and current delivery, On the lowend the PL will make my Legacy Focus SE beg for mercy, These are a boomy speaker and you need an amp that is merciless in its abiltity to control those dual 12-inch woofers, Mids? I did not hear much of change. They are already outstanding in the stock stereo configuration, In upper mids and treble, I hear more sparkle and bite. Overall, running them in mono versus stereo, the EVO 400 become a more accurate versus a syrupy sounding amp. To my ear, the mono configuration brings out what is on the recording to a sharper focus. Has more detail, better delineation of the instruments, and the transients start and stop on a dime. The drawback for me is the top end gained more bite. That is due more to the KT-150 than running them in Mono. If i stuck with an EL34 from Gold Lion or Mullard that may not be the case.  Nonetheless, if you have a good local dealer. I suggest you ask if you can audition a second one at you home and see what you think. Given my tastes, I like the sound of the EVO in mono better than stereo. My speakers love the additional current delivery. That may not be the case for you, and I would hate for you to spend another $5300 on something that you feel did not do much to improve things, Wish you the best. 

Thanks. That was informative. Since my PL stereo setup is augmented with a pair of REL S812's, it may be that a mono setup would be overkill.

Consider a Zesto Audio Bia 200 Select on the used market for considerably less.

@ vinylvalet: Owned a pair of Eros 300's the Bia would be going backward. I love the sound of Zesto gear. The 300's were the best sounding amp I ever owned. However, being a full-on Class A design, they run too hot to work in the space I have for them. Perhaps one day if I move to a house that has a larger room where I can let them breathe. The PL also run hot but being push-pull, they do not get nearly as warm as the Zesto.