I would try the Yamaha receiver powering your new speakers before you make any additional investments. If you have a small to medium sized room and listen at reasonable levels, then the receiver will probably have plenty of power.
If you decide to add an amp, then Emotiva is a good option. To save a few bucks, you could also get a pro-amp like the Behringer A500 (<$200) to drive the mains and let the receiver handle the ceter and surrounds.
I have to disagree again. With most speakers I would agree, however Dynaudio, drivers are significantly different. They have a motor system that is unusual, although copied by Morel and Jantzen. These drivers are small, yet they have have voice coils 2.5 inches in diameter. This makes for a heavy voice coil. The reason the dust cap is so large is because it goes over the voice coil like any other speaker. This also contributes to the speaker being 3db to 4db less sensitive than most other drivers, and a lot less sensitive than some others. So right off the bat you need twice the amp power than for other speakers. To add to that, the relationship of phase and voltage of these drivers makes much higher current demands on the amp than you might appreciate.
So why bother with these drivers? And they are among my favorites.
Well they have an excellent frequency response and off axis response. You can design a crossover first order low pass and usually second order high pass that has a really smooth response in the crossover region, with minimal phase and time delay issues. This produces an wonderfully smooth open sound.
These small drivers have an excellent bass response.
The over sized voice coils result in a robust reliable speaker with minimal thermal compression issues.
I have designed and built the following speakers with these drivers.
http://mdcarter.smugmug.com/gallery/2465549_x3u39#129315000_LjFX5
http://mdcarter.smugmug.com/gallery/2465549_x3u39#129314808_iV8xY
http://mdcarter.smugmug.com/gallery/2465549_x3u39#129312026_7G6qa
The first speakers were built for monitoring of location live recordings, done mainly for public radio outside concert broadcasts. They are now my surrounds powered by Quad 405 II
The second speakers also built for monitoring of live recordings. These are now in our town home in Grand Forks.
The third used the mid range Dynaudio M75, still with 2.5 inch voice coil for midrange biamped at 180 Hz to the KEF B 139s. These are now re aligned and my rear surrounds, and the surrounds for Multichannel SACD. Currently they are powered by two Quad 405 IIs
Here are my powering experiences.
When I built the top set I restored a tube Dynaco, 20 Watts per channel. They barely drove them above background levels. The Quad 405 II amps 100 watts per channel drove them pretty well, but you could still clip on the fortissimos without them being excessively loud. That is what they were powered by in the space in the photograph. To really make them open up and perform required the Quad 909 250 watts per channel. Both the 405 II and 909 have excellent current reserve.
While using them for monitoring, I had a chance to record a number of famous musicians giving concerts at the Chester Fritz auditorium. The musicians were highly complimentary of those speakers.
The second speakers are now driven by a couple of Quad 303 amps, 45 watts per channel. One of the 303s just drivers the isobarik coupled cavity bass system in those speakers. Now I use the 303s on purpose to limit the power and avoid getting carried away and generating complaints from the neighbors. In other words these speakers clip out the quad 303 fairly easily. Now I suspect those 303s will provide very similar powering to Yamaha receiver.
The top end of the third speakers were powered by Quad 405 II and later after its availability the 909. The 405 II always marginally underpowered them, even with the crossover at 180 Hz.
I really like Dynaudio speakers. They are one of the few speakers I recommend. However I have to recommend that a purchaser adequately power them.
If you have ever seen Dynaudios demonstrated at shows, they always have over sized amps and the above is the reason.
I seriously doubt the OPs Yamaha receiver will give him what he paid for from his Dynaudio speakers. However if he can get out of Yamaha how much current the amps on that receiver can dump into a four ohm load we can be more specific. To get 100 watts peak they need to provide 5.5 amps into a four ohm load to be equivalent to the quad 405 II, and as I said even that is marginal with those drivers, so more would be better.
