Mark, depending on what your upstream gear is, even the Reference series can be a bit bright at the top (although I would never use this word. Dynamic or lively is what I like to describe it as, as "bright" seems to imply listeners fatigue, which I have never suffered from with these speakers). With that being said, two great combo's from what I've heard are Parasound and Rotel...both are slightly warmer amps that would tend to blend perfectly with the characteristics of the Paradigm 40's.
I have a set of 40's and an Anthem MCA-5II amp. I cannot comment on the synergy of the two however as I currently lack a processor to tie everything together and my listening experience with this amp is VERY limited so far. Too early to tell if I'm going to like the end result.
I use the amp section in my Denon 5700 and it works very well. I've also listened to Rotel, Parasound, & Crown (K2) a good bit in this system. The Rotel and Parasound were different but not necessarily an improvement over the receiver. The K2 added some pop and impact and (IMO) was sonically superior to the others. Unfortunately it's now being used to drive my subwoofers. A K1 would be more than enough for the 40s...
The Rotel RMB-1066 is a nice little AMP. Currently I have one powering my entire setup(Paradigm Mini's F/R / CC-350. Hasn't winced once with everything I've thrown at it.
I'd throw in a vote for Rotel, specifically the RMB 1075. I'm using it with my 40's and it definately "sweetened" them a bit. I've used Denon, Yamaha, HK, B&K, and so far the Rotel has impressed me the most.
Mark:
IMHO, the Anthem MCA series are a shoe-in for the 'Digms. The Active/40's, in fact, used the same amplifier technology. Anthem is in the same group of companies as Paradigm, so I am sure the Anthem engineers are listening to Paradigm speakers.
I've heard the combo, and it is deadly! The MCA 5 Series II is still available and is an excellent choice at a great price. The new series (MCA 20, 30 and 50) are also available. They are a bit more expensive, but my limited listening so far has proven that they are worth it.
Definitely give them a listen.
/Jeff
I tend to find that the anthems make the paradigm refs sound 'bright'. I also own a pair of active/40's and I find that they tend to be slightly bright too, especially when listening to pop music.
If your room has mostly hard surfaces, I would recommend an amp that rolls off the upper frequencies, such as the rotel or parasound.
Mark, the last two posts prove to you why you have to do your own auditioning when it comes to amps. Take these recommendations, but please listen for yourself before buying!!!