Benefits of brand synergy

I would match power amp, speaker cables and speakers first, and the rest "doesn't matter", in a manner of speaking. But if we are talking reference level components, let's say, Gryphon, Lamm, Rowland, I would certainly try all possible preamp/amp combinations and would likely like them all. But they would sound different, I might even prefer different combination for different music, like different cartridges you know.
Of the brands that I just mentioned my first instinctual move would be to try Gryphon preamp with Lamm power amp and Rowland preamp/amp combo. Don't ask me why, I don't know.

"Don't know too much about Naim, but is it possible to use Naim with non-Naim?"

Yes it is. It used to be and still can be a pain in the rear end. For the longest time, Naim only used DIN connections (except for turntable inputs). They now have DINs alongside RCAs. However, the DINs still sound better, going DIN to DIN from source to preamp, and pre to power. I'm not sure if their power amps have RCA inputs though.

Their preamps must be run by either a Naim power amp or Naim external power supply, as their preamps don't have an internal power supply.

Naim sounds best with Naim IMO, due to the DIN connections and star grounding (basically everything gets grounded through the source).

I've heard Naim amplification with non-Naim sources and vice versa, and it almost always sounded off for some reason. The sum is always greater than the parts to my ears. The only non-Naim digital sources I've consistantly heard sound great with Naim amplification is Rega. The Linn LP12 sounds right at home with Naim stuff too.

I've only heard 2 Naim speakers I'd ever own - the Ariva and the current Ovators. Wouldn't pair them with anything other than Naim though. I'm a big fan of Naim, but can't get passed their speakers. Too dry and wall of sound to my ears. I've wanted to like a few pairs, as they do a lot of things quite well, but I just can't listen to them for more than a half hour before I'm looking for something else.

I own a Bryston B60, as I think it does the PRaT stuff just as well, and adds body, detail, imaging and soundstaging. The best of all worlds IMO.

I try to stick with one brand whenever possible and even try to determine what speakers and cabling they recommend as well. I figure its best to ask the engineers after all. ;)