As you are aware, system matching is important, but also a matter of personal taste. Your budget allows a lot of flexibility. While maybe not being as specific as you might want, I will give my impressions of varying equipment with the B&W Nautilus series. I am only commenting on what I have heard--so many of the things on your list are left out.
Krell: Great bottom end, but the top end can be a little harsh with the B&Ws. For your musical tastes I would probably not go this route.
Bryston: Very reliable, excellent build quality, but not the end in fidelity. These are great efficient class A/B amps that can really rock--not what you want to do I think. In your price range I think you would be happy with something else.
Sonic Frontiers: It was some time ago that I heard this combination. It should be carefully considered. Tubes can be a lot of fun if you take the time with them (they can be finiky). I listened to it on 802s not 803s and while I'm guessing a bit I think the 803s might need a little more power than the power 2 offers.
Cary: I have not heard this particular Cary with the B&Ws, but I own a Cary 40M signature that I have listened to with 805s. So my comment here should be taken with a grain of salt. The imaging and presentation are really spectacular. I like the sound of the Cary amp very much, it's a colored sound--not the most neutral--but very inviting and very 3 dimensional.
Levinson: This is probably my favorite combination overall. I have not actually heard the 383 with the 803s, but have heard the 300 series separates, so it should be close. This to me gives excellent soundstage, dynamics, it's not harsh. It plays a very wide range of music equally well--unlike the Cary which I tend to prefer for softer types of music.
Linn: I haven't listened to this with the B&W, but have found that Linn equipment tends to work best with other Linn equipment. It's less mix and match friendly, at least it has been the few times I've tried.
Classe: This is one you did not mention that I feel is worth mentioning. Particularly the older amps. Model Ten with the 803s would be a great match. Smooth presentation, very dynamic, no harshness, good imaging (but not as good as the Levinson). I'm less familiar with their pre-amps.
Well, those are my opinions--I'm sure you'll get some that vary quite a bit. Good luck--when you do make a decision please post it and your findings after break in and listening a while.
Krell: Great bottom end, but the top end can be a little harsh with the B&Ws. For your musical tastes I would probably not go this route.
Bryston: Very reliable, excellent build quality, but not the end in fidelity. These are great efficient class A/B amps that can really rock--not what you want to do I think. In your price range I think you would be happy with something else.
Sonic Frontiers: It was some time ago that I heard this combination. It should be carefully considered. Tubes can be a lot of fun if you take the time with them (they can be finiky). I listened to it on 802s not 803s and while I'm guessing a bit I think the 803s might need a little more power than the power 2 offers.
Cary: I have not heard this particular Cary with the B&Ws, but I own a Cary 40M signature that I have listened to with 805s. So my comment here should be taken with a grain of salt. The imaging and presentation are really spectacular. I like the sound of the Cary amp very much, it's a colored sound--not the most neutral--but very inviting and very 3 dimensional.
Levinson: This is probably my favorite combination overall. I have not actually heard the 383 with the 803s, but have heard the 300 series separates, so it should be close. This to me gives excellent soundstage, dynamics, it's not harsh. It plays a very wide range of music equally well--unlike the Cary which I tend to prefer for softer types of music.
Linn: I haven't listened to this with the B&W, but have found that Linn equipment tends to work best with other Linn equipment. It's less mix and match friendly, at least it has been the few times I've tried.
Classe: This is one you did not mention that I feel is worth mentioning. Particularly the older amps. Model Ten with the 803s would be a great match. Smooth presentation, very dynamic, no harshness, good imaging (but not as good as the Levinson). I'm less familiar with their pre-amps.
Well, those are my opinions--I'm sure you'll get some that vary quite a bit. Good luck--when you do make a decision please post it and your findings after break in and listening a while.