In my experience the easiest way to get synergy is to use the same brand electronics, integrated/CD player or pre/power amp, sometimes even the CD player there as well. Though probably not admitted manufacturers generally have a "house sound" or sonic signature particular to their gear. So usually these mesh better with each other. Or, if going to mix try to find other gear with similar sonic characteristics. This is general and as most things in audio, subjective. Sometimes different brands may work together but unless as you are looking for, some one putting it in writing, it could take a lot of experimenting and expense to find different brands who synergize.
In addition, if you like the sound of a brand of amp, why not get the same brand CD player to capitalize on that preferred sound. Why mix in another brand that could take away from the original sound you liked? In my case I use Conrad Johnson amplification, they are not much into offering digital playback, so my pre/power are the same but I had to find a CD player I liked. I personally wouldn't consider another brand of pre or power amp though.
