Basic surge protection with some noise filtering without strangling the amplifier?

Well, it’s early hours for the Furman Elite-20 PFi, with the 625 V2 and a REL Carbon Special plugged in to it, but I thought I’d report back that so far I notice no SQ or performance degradation whatsoever — with a decent range of my usual music, although have not tried any classical yet.  And it is nice to have some peace of mind should there be some building electrical system (elevator motors, HVAC, god knows what) surge or other issue that my much loved Rowling is more protected than it was. 

Thanks again everyone for sharing your experiences, hard-won insights & knowledge and suggestions.

I own the Furman Elite -15 PF i. I bought it primarily for surge protection and with the hope it would not make my system sound worse. I didn't necessarily expect it improve the sound of the system.

Listening to my system after installation I thought the Furman improved the sound. I wasn't certain whether it was just my imagination. Later that evening, my wife, who enjoys listening to music with me and has a good ear but is oblivious to my equipment - mentioned that she thought the system sounded better. 

So I would recommend the Furman for surge protection. You may or may not notice an improvement, but I don't think plugging your amp into it would hurt the sound of your system. And by the way, it provides very good protection in my experience. Experienced a bad power surge and the Furman shut off before any harm came to my tube amp (tube amps can be especially vulnerable to power surges). Turned the Furman back on and everything was fine. Best purchase I ever made.

Thank you @jrsyby. Your aim was exactly the same as my current one.  And good to hear there might even be chance of a small improvement.  (I’m so happy with the current sound that I certainly won’t be disappointed if all the Furman does is protect my amp and subwoofer from surges that may never materialize; if i get some slight sonic upside, well, that is, as George Fennemen was fond of saying, “gravy.”)

@kirkwallace if you can find a good deal on a used Shunyata MPC-12C or something similar that has the outlets you'd need, I'd jump on it in a heartbeat.  I had the good fortune of running across one for $650 on a similar site to this.  I have not been able to plug my amp back into the wall.  Everything goes into it.  Great for multi use scenarios where video is involved as well.  20 amp connection.  If you can afford to get a nice used one with the furman and compare and sell the other or return, may behoove you.  The used market can give us some amazing deals sometimes!  That thing, to my ears, sounds almost as refined as the gemini-8.

I'm not sure exactly why the Shunyata gear has been so invaluable to my system.  I don't have time to suss out all the gremlins possible and have made some notes for my next build regarding wiring to hopefully address some issues I've had.  But in my treated area especially, there's no question it's a huge difference feeding my gear into the Shunyata Gemini or MPC-12 vs a normal surge protector or outlet or even into something that says it's a power conditioner but costs like 100 bucks.  It's not even close