What's a good AMP to drive my 803 N?

My vote is the Mcintosh MC352. More than enough power to make the N803 sings. You can find one around 2500-3000 on Audiogon. What other equiqments do you have?

Along with the Mac, recommended above, I found Rowland to be a very nice match. I believe B&W purchased Classe, so that would be another avenue to pursue. Just be sure it is a quality amp with at least 150 watts or you will not get great results with them. Do a search, this exact question on the N803's has been asked several times.

I don't have anything yet. : )
Just have an Yamaha V3300 receiver.

Any recommendation for cables?

Simaudio is worthy of your consideration. Very nice in combination with B&W. I'm a fan of Kimber Kables with my B&W speakers - very satisfied.

I've got the CDM9's. Not quite as nice as your 803's. I just slapped some Krell gear in front of the speakers. Sounds great! Clean, smooth, articulate and detailed w/ great controlled base. The Krell electronics have completely transformed my speakers. I'm very pleased with the Krell/B&W sound.