which amplifier best for von schweikert speaker?

I have the VR4 Jrs. Von Schweikerts are very linear and neutral and efficient so compliment them to your taste. The NuForce 9 are dynamic and detailed with deep bass but not a lot of drive, the Moscode 300 is gorgeous and liquid and again not a lot of drive, the LSA Standard (integrated) is clear and detailed, dynamic with loads of drive and built like a tank, the Cayin A88t is sweet and liquid with the right tube compliment with amazingly good bass and quite dynamic considering how low the power output is. Though I've never owned it, the Plinius SA-50 is a splendid solid state amp, no grain, detailed, sweet, liquid mids with great bass detail and drive. (Just a word on Moscodes: The older 300 and 600 concept was based on a Flutterman design that was transformer-less and so the earlier Moscodes had small output transformers and for that reason not the kind of dynamic drive you can expect from a solid state or good tube amp (the Cayin has enormous output transformers). Even though I've never heard them, the newer ones have larger transformers. These old Moscodes, as I imagine the new ones to be, are truly remarkable amps, gorgeous, classic tube sound with excellent clarity and bass definition. It's the number one component, I regret selling.

Funny you should ask this, since one thing I remember well from one of the NYC H.E. shows was the VS room, where a pair of the 4JRs was sounding just okay with a large integrated, but the same speakers sounded incredible down the hall powered by the Moscode amp. I actually went back to the VS room and told them to go down the hall and hear their own speakers with the Moscode amp. Apparently, lots of showgoers had told them the same thing!

Anyway, the Moscode is a hybrid design with tube input stage and SS output stage, and even the old model I heard listed for $5K, so even used, it might be a stretch. That said, I am an Odyssey Stratos (HT3) owner myself, and can vouch for these wonderful amps, and Klaus Bunge who runs Odyssey Audio. I've had the amp about five years, and I have been pleased with it - smooth, detailed, powerful, dynamic and quiet.

Other amps I would look into in your price range would be the Vincent Audio SP-331 (also a hybrid), any of the Belles amps if they are in your price range, and the Butler hybrids, if you can find one used.

One thing I would do in your situation, focus on a two-channel amp. You'll get the biggest bang for your buck. Keep the B&K for the center and surrounds, since you have no complaints about the surround sonics.

I use a Parasound A21 with Von Schweikert VR 4JR speakers and have been pleased with this combination for both music and movies. You can find used A21 amps under $1500. There is strong demand for used Parasound A21 amps, so you should be able to re-sell it with minimal loss if this does not float your boat.

I owned a pair of VonSchweikert VR3's a year ago. The amp that really made them sing in my room was the Odyssey Stratos. Usually found on these pages from $500 on up. No transistoritis whatso ever.
I'm sure it will out perform the B&K. The Stratos is a 2 channelhigh current amp and you can get them in monoblocks too. Bryston amps are another good choice. You simply can't go wrong with either of those. I have a friend that is using Rogue's big tube amps on the VR4 and my local dealer used Ampzillia 2000 monoblocks with very good results. But I don't think any of them actually was that much better than the Odyssey.