Bright(to me) usually means the highs are overexaggerated. Usually that ends up causing ear fatigue(ears ringing), headaches and other things. Generally the high frequencies are causing extra sss's in the sound or what people might call sibilance.
Loud and ear fatiguing are not mutual. I know several speakers/amp setups that can play loud yet never be fatiguing to my ears.
To ME: Amp and speaker matching are like baking a cake. Some might prefer the way it tastes, some don't. Just have to find the right ingredients to make the taste contour to your tastes. Are the differences drastic? Not really but its all about flavor
As far as what I'd personally recommend. 2 of my friends own Klipsch's. 1 uses Sony's DB series(which is now the 1es or 2es) and the other uses Denon. I've heard the Denon Klipsch setup several times and its not as fatiguing as it was before he swapped receivers from his former Sony 50es.
So my suggestion is to listen to the following recievers:
Marantz
Denon
NAD
Rotel
HK
Marantz and Denon are very similar and have lots of features(you may not use). NAD has very few frills but all the basics and a killer amp. Rotel is a higher priced option but offers all of the above of the Marantz/Denon/NAD choices. H/K has a decent feature list + what I'd call a warm sound. They run 500+.
If I was going a receiver again I'd go NAD because its rock solid and amazing sound. I think they list about $800-$1k. If you can't spend that much, I'd either save up more $$ or go with a Denon 2803/02 or the Marantz.