Naim and Denson amps

I'm looking for power amplifiers to use with my Mark Levinson 390s CD player/preamp and B&W804N and HTM1 fronts. I'm considering Naim (probably NAP-250, 2x80) and Denson (probably Beat-300XS, 2x100, Beat-350 monoblock, 1x125), and a used Boulder 250AE.

Will using a Naim power amplifier with anything but a Naim pre-amp be an issue? Also, I thought about using Naim for my mains, and a Beat-350 monoblock or Boulder 250AE for the center channel. I don't have a chance to test any of this equipment in my home, but buying 2 of the above brands would allow me to listen over a period of time, and I could upgrade to all-Naim, all-Beat, etc., later, or just stick with what I have if it works.

Can anyone give me advice? I've only had a chance to hear a Naim 250 and 300 in the store, and I loved them, but they were paired a with Naim pre-amp. The Naim-145 might be the way to go for center channel, but the Densen will be cheaper, and give me an alternative upgrade path to consider. If Naim power amps don't work with other brands, I could go all Densen now, or Densen mains and Boulder center..

Also, the Naim dealer told me that the preamp section of the ML390s is not a good solution (that it was only a volume gain control), and that I would be MUCH better off with a dedicated preamp component (presumably Naim, but any brand would be better than none). Does this make sense?
I want to add a couple commments to my above question:

1) Sorry, I should have stated the ML no.39, not the 390s. I checked a number of reviews, all of which stated that the pre-amp volume function in the ML generally superior to using a separate pre-amp, even using very high-end preamps, such as the Lamm L2 or the Audio Research Reference Two Mk II. Could there be something particular about Naim components which meant using a Naim pre-amp would produce a better sound? If so, at which model/combination of Naim pre-amp/power supply would I start to see an improvement, e.g. Naim 202, 282, 252, 552, etc.

2)Maybe a simple way to address my above question, given potential price difference between Naim and Densen equipment is, "at which price point does Naim equipment begin to definitely outperform Densen, and in what way?" The top end stereo Densen Beat-300XS amp is about US$3700 (the Beat-300 is about US$1100), while Naim amps range from $2800 (NAP-200), $4650 (NAP-250), $9850 (NAP-300), $23,950 (NAP-500). I read in many postings that many people switch from Naim to Densen because of similar sound quality (I often read better transparency)...which amps are being compared exactly?

Sorry for these 2 long posts, I hope this clarifies my questions.
I auditioned at length a pair of Densens: the 200 preamp and 300xs amp, playing Davis (French company) speakers (which i also heard with other gear and know they are pretty neutral). The Densen's have a very definite sound of their own IMO. As soon as I heard them, they were different than 90% of systems I have heard. They sounded fairly dark and laid back and had soft transients which made them very easy to listen to but ultimately, I think they ought to be faster and more dynamic. Perhaps with different speakers they would have been better but they must be auditioned before you buy (or buy used).

I have yet to hear a Naim system so I can't comment on them but if you are interested in Densen, I would highly recommend you hear them first because they aren't typical in sound type. I actually liked them but some people would find them terrible (the dealer concurred with me). Good luck! Arthur
Hmmm, shows how subjective it is. I have a B-100 with Green Mountain Audio Europa speakers and if anything the setup is a little on the bright side of neutral. Dark and soft are the very last words I'd use to describe my densen amp. Transparent and ruthlessly so are descriptions I'd use.
I also love Densen gear and the sound. Although I'm not using it now, I did not sell the B-300/B-200 pair I had been using prior to my current setup as I didn't want to part with it. Still using the B-100 for my upstairs speakers (Harbeth's) which are sounding great. I would agree with the previous post regarding the unique sound of Densen, although I'd be hard pressed to determine what common descriptive phrase I'd attach to their particular sonics. I do consider it be very 'musical' gear and think that Densen's claim of high 'air guitar factor' is pretty much on the mark. Very nice gear...too bad it doesn't have more recognition in the U.S.