First, if you buy smart, you can get the B&K 507 S2. One if for sale as of today on Audiogon for $1750 (this is about half price off new and is a very good deal). Note, I am not selling this unit, just happened to see it.
I have a 507 S2 and I compared it to various receivers (Rotel, Denon, . . .) all in my home. At the time I was using B&W speakers and now run Totem speakers. I chose the B&K as it seemed to do better in 2 channel (my primary concern) than the others.
I have heard very good things about the Arcam's (300 and 350) for the same reasons I chose the B&K. I was not able to listen to one of these with my system, but they are well regarded with many forum submissions liking these as much or better than the B&K.
My experience with the B&K:
With B&W speakers - excellent sound in stereo, seemed to me like very good sound in HT (I was not very knowledgeable in this area). With the Totem speakers, the receiver is a bit bright on the upper end. I had installed a Cal Audio tubed DAC which helped siginificantly with this and the totems.
The B&K offers a lot of flexibility in set-up and programming. It offers some controls for room problems (which I have not determined is good or not), but it is available if you have major room acoustic problem it will probably be nice.
The B&K is fairly easy to install and configure.
Plenty of power for my room (12' X 18' with a 9 to 12' cathedral ceiling)
Great remote control - best I have worked with
I like the zone 2 set-up on the B&K, although mine is not hard wired for zone 2 (they come either hard wired for zone 2 or for channels 6&7). If you want to run zone 2 and it is wired for channels 6 & 7, you have the choice to use an additional power amp or take the unit in to an autorized B&K dealer and they can change the jumpers/wires (I have not done this as my B&K dealer in Kalamazoo Michigan is clueless and state that it will take them a month to do this!)
Processing? It seems to do a good job and has the latest formats covered (no video upconverting - not an issue for me as my TV has tons of inputs). I would not recommend sending video through any receiver - period! This is just my feeling.
All in all, I don't think you would be disappointed with either the Arcam or the B&K. I hear the Arcam is a bit more laidback like a UK based component. I find the B&K more forward and even bright with my new speakers.
FWIW: I now have a Conrad Johnson MF 5600 5 channel amp that I use for my front 3 channels and my zone 2 speakers. Initially, I was just looking for a zone 2 power amp (my tubes didn't have enough juice for my speakers in zone 2) and found the Conrad Johnson which I feel has been musical performance than the B&K.
If there are more specific questions and want more details, feel free to e-mail me directly or send me your number and I can give you a call.
Based on your metric use of measurements, I am guessing you are not in the States. Not sure whether that plays any role. B&K service from the company is excellent, replies the same day with detailed answers to any questions.
I think both offer free software upgrades (I know B&K does, and they are fairly easy to do). The remote also can be modified and comes with a CD rom for changing the screen layout, etc. . . Convenient if you want to label different inputs, etc. . .
Check out the used 507, at $1750 it is a very good buy.
Ckoffend