What qualities do you look for in a good amp?

Can you name them as well?
I would first have to know what speakers they are to be mated with if I was going to aim for the best synergy.

I would then research what others have found to be the best match with the speakers I will be using.

I would then go and try to get an audition of the amp.

Lack of grain

Those are all points I would listen for to see weather I like the presentation before purchasing.

Good luck!
Hmmm, I am not into silver yet, so I look for black faceplates. =)

This is like asking literally for "ice cream" when you walk in Baskin Robbins.

Seriously, I try to "listen" more than look. I will "look" at the spec sheet but that doesnt mean much. I like to look inside and see large and well constructed torodial power supplies, first and foremost. Then all the other "guts" like, voltage rails, cabling routing, Caps, boards, output terminals, output devices, etc. etc.
I think of a power amp as the producing element in my system. Preferably it will be the strong, silent type which can execute the most demanding of tasks without complaint or hesitation. Extending the analogy, the front end source component is the talent and the preamp is the director. The rack, cables, cords, spikes and room treatments are the props. The speakers are the stage.

My decision tree when auditioning a power amp flows from one must-have aspect to another. It begins with philosophical considerations:

1. Solid-state. For me, this is a cost, stability and reliability issue. If the best tubes were perfectly matched and cost the same as sparkplugs I'd reconsider.
2. Reputation. I take comfort believing there is a designer behind the product with experience and talent. An amp's popularity is a plus.
3. Pleasant appearance. The amp must look purposeful. Flimsy looking or unfinished parts convey weakness in execution.

Physical considerations:
4. Rows of external heat sinks. These are reputed to be expensive. Mounting them on the outside of the chassis seems to be the preferred method.
5. Sheer weight. Real-life power supplies are heavy. If it specs at 200 watts a channel but weighs only 25 pounds somebody's kidding somebody.
6. Number of output devices. More is better. While I admire an amp that can squeeze alot of performance from a minimum of parts, in the long run my money's on the unit that has so many muscles it never breaks a sweat.
7. Connectors. With the amp in place they must be reachable and not too difficult to tighten. With its own allure, gold plating is the icing on the cake.

This subjective element is the hardest to pinpoint. When an amp is doing its job for me, it will sound smooth, effortless, unforced yet unrestrained, balanced, limitless, fast, quiet and balanced. All combined it will sound magical.

Enjoy your search.
Look for an amp that doubles it power (watts) as the ohms are halved. This is a sign of a stable amp that will drive almost any speaker load.

200 watts @ 8 ohms
400 watss @ 4 ohms
800 watss @ 2 ohms etc.,etc.

Like Rockvirgo said, the heavier the amp, usually the better... this translates into a larger power supply and more $$$.

Short list to start with: Audio Reserach, Bryston, Krell, Mark Lenvinson, Pass Labs.(only to name a few) These are all high quality, well made amps, by 1st rate manufactures.

The final choice is what sounds best to YOU, not the BS the salesperson tells you. Good Luck!
I like the ones that just get out of the way.This is one that changes the signal the least from input to output. I like the romantic sound but not on every recording.Quiet is a major plus...no hum in the speakers. So far the ones that seem to do this the best IMHO are digital amps. They don't weigh much but are 50% more efficient than the average amp.Which means they only take in what the speakers need.Instead of giving half of their stated power to the atmosphere in the form of heat.

Good Luck with the Hunt
I agree with rockvideo.Let me add some specifics.Some of the amps mentioned by Ig40 did not work for me.You need an amp with big dynamic range no feed back and reputed to be reliable.I have been happiest with Gryphon and YBA amps.
All excellent responses. There are many factors that go into purchasing an amp. You have to ask yourself a few fundamental questions.

1. How much power do I want?
2. How much heat do I want to put up with?
3. How much space do I have for the amp?
4. How much do I want to spend?
5. Tube Vs Solid state Which sounds better TO YOU!!
6. Do I prefer a neutral sound or a euphonic warm sound?
7. What are the other components in the system and how can
system synergy be achieved?

If you aswer these questions honestly you can narrow down you search to a few manufacturers and then auditon them!!
What to look for. No particular order.

1) Customer service dept readily available.
2) Stable reliable company.
3) Few models used up for sale.
4) Input impedance high enough to allow use of tube pre-amp.
5) Power rating stable into 4 ohms.
6) Protection circuitry that prevents failure due to clipping.
7) Ability to throw up a open sounstage and image precisely.
8) No excess energy in the bass/upper bass/lower midrange.
9) Highs that sound real without ripping your ears off.
10) Tonal accuracy in the midrange that produces palpable voices.
11) Binding posts that allow use of spades/bananas/bare wire/bi-wire.
12) Adjustable input sensitivity.
13) Reliable proven design.
14) Balanced circuitry that is truly differential.
15) Good resale value
16) Available in black or silver. No glitzy appearance.
17) Moderate heat to keep your room cool in summer.
18) High dynamic headroom.
19) Quick warm up time- under 1 1/2 hours to enjoy the sound.

Anything else??
I too was on the "Truly Balanced" path, courtesy of my Rowland Model 2. I even worshipped at the portal of "BPS" (battery power supply). This amp was "IT" for me.
Then I heard an Aleph 3. Class A, single ended, sounds funky on warm up. Heats the room. But on my Apogee Mini Grands, my Montana SPIIs, and my custom 2 way monitors, the Aleph amps sound better than anything I've tried.
Class A means NO headroom, that's OK, I have never clipped my Aleph 2s on my Apogees. 160 watts Class A does not sound at all like a 200 watt class A/B amp. It just sounds better.
I also own an Adcom 5500 stereo amp, this is THE most underatted amp available today, in my opinion. It runs quite hot for a class A/B amp. Nelson Pass had a hand in it's design, & it shows. You can try one of these used for around $600.00.
I've gone over to SET amps, so what I look for isn't so much technical as musical. A liquid midrange without being syrupy, a smooth, sweet treble, and adequate bass extension are fundamentally important. Palpable imaging goes without saying, along with a sense of realism and naturalness. On the technical side low noise is a must, given that the speakers will be quite efficient, and adequate input sensitivity to mate with my favoured transformer passive line stage.
A pretty face, a great rack, and a nice round caboose.
Insightfull answer Gunbei! Let's not forget that all important, head...room. Time for Football!
A nice, thick brushed metal faceplate with deeply engraved logo, and some really slick blue lights and LED's....oh, and those big, gnarly gold-plated terminals out back.....yeah, and those analogue meters to let you know how much g-force they're pullin'. And they gotta be real big and heavy so they aren't dwarfed by my thick, long speaker cables and power cords. Lot'sa them sharp cooling fins too to make it real stealthy looking. And it's gotta cost a butload of cash too, at least as much as your car...braggin' rights and all you know. Oh, and as a consession to my wife it has to go with the wood floors and leather couch.

Yeah, that's the ticket!

1. Highest possible performance

2. Doesn’t blow up very often.
Thanks to all the posts - it helped me - now I expect more from an amp, which is a good thing for my futere hifi experience. I will try to look for the qualities you all suggested.
I do hate it when they blow up too often. You just get the air cleared, and there it goes again!!!