Best way to compare amps?

Hello all. I'm getting ready to compare two ss amps and seeking advice as to what would be the best way to compare. Should I listen to one for a couple of days and then swap the other one into the system? Any tips would be appreciated!
The best way is to combine both. First you kind-of A/B switching between each other and than listen one after another for couple of days.
I would suggest listen to them for a couple of weeks ea. minimum because you have to both let it run in with your system & also audition under varying circumstances which include different times of the day. Also you might want to experiment with/without power conditioners & PC's if you have them. Good luck & let us know your results!
A couple of days would be better than a short period. If you can swing it try a couple of days each. At minimum a couple of hours each.

Sometimes you have to switch back and forth to appreciate it. I remember when I changed my NAD 3020 for a Mission Cyrus 2. At first the Mission amp didn't seem so much better. After a day I put the NAD back and whoa .... what a difference in dynamics, soundstage. The Mission amp went straight back in and the NAD was sold the next week.
An interesting observation that I've noticed when A/B 'ing ALL TYPES of audio gear. (Seantaylor99 alluded to this fact!) Sometimes, It's tough to notice an improvement in audio quality. But when going back to a lesser sounding piece of gear, the difference in lower audio quality jumps out quite clearly! Seems that most people find it easier to hear a degradation in audio quality than an improvement! Happy Tunes!
If you have some extra speakers and cables, then leave the other amp turned on in another room, so it is warm when you make the switch. A cold amp is going to give you a bad first impression against the other one. Many amps take a couple hours to get up to speed from a cold start.

I am guessing that part of the reason Sean above did not think the Mission was better at first is because of a cold amp (and switching back to the NAD).

You maybe can just leave the other amp on with nothing connected to it, but I am never sure if this is good for the amp.

What Fatparrot is saying was my experience with power conditioners and speaker cables. May help explain why some claim they make no difference at all. They plugged in the conditioner or new cables, heard no big immediate difference and gave up. I also had the same experience with my REL sub. When I shut is off after having it for a while, I thought: "Where did the music go?"
Sugarbrie ... I don't think warmup was the reason. Warmup may make something of a difference bu nothing as profound as what I heard. I think fatparrot is close to my experience. You may not notice the step up, but boy do you ever notice the step down. This applies to many other areas of life too.
I was just guessing Sean. Comparing warm components is extra important if you are not making an upgrade, but are trying to choose between two equal amps and you do not have the luxury of weeks to get a feel for them. They both sound great, but which one do you buy? I try to avoid going to an audio dealer when they first open. Everything is cold, including my brain. I also usually go back more than once before getting out the plastic.
Thanks for the replies. The amp I'm auditioning , if everyone is curious, is the Innersound esl amp and comparing it to my Odyssey Stratos amp with cap upgrade. The rest of my system consists of: Cary 303/100 cdp -> Coincident cst ic. -> Rogue 66 lsr -> Coincident cst ic. -> above amps -> AP Oval 9 biwired -> Magnepan 1.6qr. Sounds like I need to audition each one for at least a week each. I'll post my results later on. Thanks again and would like to hear any more input!
Bradz, please let us know what you think after comparing. I'd be very interesed in hearing what you thought.
Hi Brad; Of course both amps should be broken in, ie demo or used as well as warmed up. If you start introducing other variables in the comparison, ie ICs, spkr cables, power conditioners, and power cords be sure and take good notes as you go along. The more variables you introduce the longer it will take and the more complex it will become. But then one amp may sound good with one combination of wires, but the other may sound good with other wires.

Of course this could drive anyone crazy. If you're pretty comfortable with the quality of your "wires", I think it would be best-- and certainly easiest-- to keep everything constant except the amps. If you have the option, using each for several days would be a great test. Good Luck. Craig