What is your real question Don?
Do you want to know whether a random Class A amplifier will sound better than your current Sony Tan-80ES Amp (which sounds "great" to you)?
Or, do you want to know whether $2,000 is an appropriate price for a used Krell KSA 200 Amp?
Can you give us some background on why you would " Love to buy a Class A Amp"?
What is your price range and what do you wish to accomplish with your system by purchasing a Class A amplifier?
How much power do you need and what speakers are you trying to drive?
BTW, your amp is a Sony TA-N80ES and is rated at 200wpc but it nowhere near doubles power into 4 ohms, which implies it may struggle with speakers having low impedance inputs or impedance variations throughout the frequency range.
It sort of sounds to me as if you have heard that Class A amplifiers are inherently "better" than other amplifier topologies and you saw this Krell for an amount of money you can afford so you would like to go ahead and purchase it and you want a bunch of folks to support your purchase decision.
My answer is not meant to be condescending but to point out the risks of asking for "help" in spending your money from a forum where everyone has their own biases. Fortunately, you have received some solid advice from Erik and George here. I certainly agree with Erik's comments,
don't be mesmerized by a technology. Just because an amp says "Class F" or "Zero Feedback" is rarely a reason you should personally buy one or the other.Although, I would add "Class D" to his list of technologies.
I also agree that you would gain perspective by following another of Erik's recommendations,
maybe a tube amp would be worth listening toAnd, I particularly agree with his statement,
Use your ears,and don't spend money unless the differences you hear are worth the spend.However, i don't agree with his statement,
I don't think Class A is what it used to be.I have two excellent sounding Class A amplifiers here now, a pair of Lamm M1.2 Reference amps and a pair of Clayton M300 Class A amps. I also have another excellent sounding Class AB amplifier, a McCormack DNA-2 LAE that has been fully upgraded by SMc Audio. All three sound better to me than Ncore's latest Class D effort, the NC1200 modules in the Acoustic Imagery Atsah amplifiers.
So, I would say that Class A is an inherently superior topology for certain technical reasons but, like anything, different implementations will sound different. Also, because they are biased to output full power all the time, the build quality of Class A amplifiers must be VERY robust for reliability so it may not be a good move to purchase older or less expensive versions of the topology. That said, I have heard pretty good reports about the Monarchy Class A amplifiers at reasonable price points.
Regarding Class D, I would say that, at lower prices they can offer very good value. As you pay for better implementations, they can sound quite good but at the upper price ranges the topology is not capable of competing with well-implemented Class A or AB amplifiers IMO.
Go listen to some amplifiers, preferably with your own speakers or, if your Sony amp sounds "great" to you, go buy some music and be happy with the sound of your system.
Use your own ears to decide. Lots of very well meaning members here who know a LOT about audio and they base their opinions on their ears but in the end it is about YOUR ears. I like to use the analogy of wine tasting and taste buds. A great wine for you is one that taste great to you.
If a friend of mine asked me if he should buy a class A amp I would say don't do it unless you know you have to because you have speakers that really need class A. And I assume you already know that amp / speaker pairing is so critical. The best amp with the wrong speaker will still sound like crap.
Do you have a local audio club in your area. It is a great way to get exposure and listening opportunities to high end amps.
This is just my opinion, but I think I have heard probably more amps than most people on here, having been in the high end business for 25 years. Not much I haven't heard.
The absolute best amps that I have owned and heard have been Class A amps. Something special about that design. They do suck power and run extremely hot, (the hotter they are, the better they sound).
However, I do agree with the comments above about hearing them in your own system, in your own room, with your own music.
May not be your cup o' tea?
Once you've lived with a "good" pure Class A solid state amp it's hard to go back even to a highly biased Class A a/b amp.
The sound just seems to envelop you from speakers with an ease, without being drawn to them, that the sound is coming from elsewhere in the sound stage rather than emanating from them.