Benefits of brand synergy

I think generally there is a ton of synergy from amps and preamps from the same brand. For sources, not so much. So I think you can have decent success from just doing the preamp/amp from the same brand but going elsewhere for the source.

I agree with Kclone, definite synergy in staying with the same brand for amp/preamp. One of the best systems I ever heard was Meridian cd/pre/amp with Sonus faber speakers. Find a brand you like and commit to it. Mix and match approach can work, but is a harder to realize maximum potential. Move up the same brand range when funds permit. Its far easier, synergistic approach.

I've had good experiences with matching the same brand amp/preamp. In one system I had with matching a McCormack TLC-1 Deluxe along with a McCormack DNA .5 Deluxe the music to me was heavenly. I also really enjoy the music with a Kavent S-33 preamp and P-3300 amp combo. To me I think the Kavent gear is supposed to work together hand in hand. I found the S-33 has a gain control. You can leave the gain as is or decrease it by 10db. From speaking to the dealers that sold Kavent they said the P-3300 has really high gain. I can't imagine the P-3300 without another preamp. I unfortunately didn't try it though. Sometimes it is the little things like that that make me think having the same preamp/amp combo is really supposed to be.

Totally agree that preamp/amp matching is the best approach. Have tried mixing sources with good results, but ended up matching the cdp as well, but only because it out performed my other.

I don't know about Naim, but usually good digital will work just fine with any brand decent electronics. As for preamp/amp, it is an interesting question which I believe cannot be answered in general terms, only on case by case basis. And also it might not be better or worse but just different. Within my price ranges I follow the path of integrated amps and don't bother about that.
Yeah, many mix brands to tailor the sound as precisely as they can to their taste. Given sufficient funds, time and patience, I would too.