I run my Yamaha NMS10's from and old  Yamaha P2100 which is 120 Watts @ 8ohms and no fans. The perfect match for the NMS10's really. 
But it has had issues with the attentuators for a long time now and often I loose one channel until I sweep them back and forth. It's dieing. 
 
Most power amps seem to have fans.. that rules them out for a studio. 
I used to use an intigrated stereo amp but all of mine are also very old and have issues. 
Also a lot of amps now are Class D? Is this a good thing? 
 
Anyhow the reason for this thread is to get some input and see what those of you who still use passive speakers are running sucessfully. 
 
As example this is one solution I found. My brother has the RR2150 and it's stunning to say the least. But I certainly don't need the radio. It would be $750 including shipping. A pair of the 2200 would be $850 delivered. 
https://www.outlawaudio.com/products/2200.html
 
https://www.outlawaudio.com/products/rr2150.html
 
 
 

I have an old Alesis RA150...no fans, totally inexpensive, and works great.  I think there are actually a fair amount of amps on the market without fans, if you start looking.

Yes it seems a lot of Class D amps being more efficient can do away with a fan.
I'm boning up on a lot of audiophile systems and of course these leads to ultra geeking!
 http://www.audioholics.com/audio-amplifier/amplifier-classes
 
This one has my interest at the lower price points
http://www.musiciansfriend.com/pro-audio/cerwin-vega-cv-900-power-amplifier#productDetail
 
 

If someone can hear the difference between decent amps, not pushed to their limits.....well...I'm not sure that's possible.  If you're nostalgic...get an old Crown D150a or similar.   For a low wattage amp, I don't see the need to spend $300 or so, unless you totally shy away from Asian made.....ya know...that big country with their name starting with a "C"

 
No 100w hi-fi amp I've seen has a fan.  Isn't class D a square wave modulated to produce the frequencies ?  Not what I'd want for the best sound.  I think it's main purpose is volume out of cheap circuitry, not sound quality.

If you follow the link I posted above it explains the difference in classes of amps. It's complicated and do not even attempt to understand it fully without a degree in engineering.  
But this I gleaned from the text: 
Class A amp can have the best overall sound but they are inefficient so they generate a lot of heat and therefore the loud fans. Class D is a newer technology and are very efficient so they  not only weigh less, they don't generate much heat therefore will be quieter and often passive.
A passive Class A amp will probably be 80 to 100 watts. My Yamaha P2100 is rated at 120 Watts and is passive but it has a huge heat sink around it and I keep my feet warm with it under my desk. 
 
Class D is what is found in modern powered PA speakers and monitors. The reason being the weight and heat of a Class A or B would not be feasible. The speaker would catch on fire. 
Sound quality can be an issue with any class of amp if poorly designed. There are certainly plenty of badly designed Class D amps. ( dare I say the B word) 
Class D works best with a feedback loop to control it and matching the Amp to the speaker inside a cabinet, bi amping and all that is what make powered speakers a very good choice.  I have ditched my passive PA system. 
 
And it is very tempting to go powered with a new set of Yamaha HS80's. They say they are a close replacement.  It might cost me the same to buy a good power amp.  
But I hate to give up my NMS10's so therefore the research. 

mixmkr
If someone can hear the difference between decent amps, not pushed to their limits.....well...I'm not sure that's possible.  If you're nostalgic...get an old Crown D150a or similar.   For a low wattage amp, I don't see the need to spend $300 or so, unless you totally shy away from Asian made.....ya know...that big country with their name starting with a "C"

I sort of agree but the trouble is I do want the audiophile quality you get with the better amps.  And true 80 watts might be enough but I've been running the NMS10's with 125 watts and it's actually just the right amount. I don't think 80 would be enough. I believe the Amp is just as important as the quality of the speakers. 
I have hooked these monitors up to some older integrated amps and it's not that good. These are respectable amps , like Technics, Sansui and Pioneer. But 65 - 80 watts was not enough. 

I have a variety of older amplifiers from Crown, QSC, Haffler, and Heathkit (yeah, you read that right!)

I've used a lot of others over the years. For the most part imperfections & non-linearities in the monitors swamp anything going on in the amplifiers. I have tried a couple of inexpensive Class-D amplifiers (in fairness this was several years ago) and I did not like them. I could hear the difference between them and the dinosaurs I own, and not in a good way.

The only two amplifiers I think I can identify - in a positive way - with a blindfold are the Heathkit and any Bryston. They sound nothing alike, the Heathkit sounds pretty, and makes most monitors sound pretty, probably not what one wants in a studio setting! The Bryston makes most monitors sound better. I can't explain it, and I'm not in a position to spend that kind of money on an amplifier, so I don't even try<G>! (Actually, NAD used to make some really good sounding amplifiers, but they had a nasty habit of overheating in studio settings, and as someone pointed out, fans are not a good idea in a studio!)

As a rule I try to avoid Class D amplifiers. That's become nearly impossible, and if you are using monitors with built in amplification I think it might actually be impossible.

But for the most part any competently designed amplifier should sound good - there aren't a lot of great new ideas in amplifier topology for Class A or Class AB amplifiers. You might be able to detect a difference between an amplifier that uses feedback vs one that doesn't, but I'm not sure which one I'd pick as "better".
 
The only thing you have to remember is that no one ever blew up a loudspeaker with an amplifier that was too big<G>! Other than that I'd just get a good Class AB, MOSFET amplifier, and there are lots of those around.

Thanks Bill, good information and more less my experiences too. I might just have to look into having the old Yamaha repaired. It is the perfect match. I was thinking there might be a way to just bypass the attenuaters. I have always run them at 3 o clock but that position died, so then I turned them up to 4 o clock now that is crackling to. I'm running out of places pat 50 % that work. 

wst3
I have a variety of older amplifiers from Crown, QSC, Haffler, and Heathkit (yeah, you read that right!)

 
I'm sure there are many people on this forum that built Heathkits. I know I did. My first home stereo amp was a HH Scott kit with "Fire Bottles". Had a great sound! When I upgraded my stereo years later, I made a tough screen protective cage for it and used it as a back up amp for my band. Our base player's amp failed one night, (it was just a filter cap) and the Scott saved the evening.
 
Walt