As a former owner of a Marantz PM8005; I can say its one IA that I wish I would have kept for secondary use in another room or location. You can bi-wire the PM8006 if it suits your taste, and even output to two subs (pre-out) if that's in your interest, but probably not necessary with the B&W 803s.
I had mine paired to B&W 603 S2s and used an Ortofon 2M Black to the PM8005 MM phono stage. My primary gripe was that combination was on the bright side. I think the tweeters in the 603s and 803s are very similar. The detailed sound stage and bass response were very good. Then one day I swapped in a pair small Dynaudios and stopped using the B&Ws for two channel audio.
I've since moved the 603 S2s to a 5.2 AV system in the family room. They're big, but an excellent fit for AV use. I sold the Marantz and moved on to a McIntosh 352 IA (not a fair comparison on price alone). BTW, the Marantz had good resale value.
Looking back there's so many really good options in the PM8006 IA space, but the Marantz PM series is worthy for the build quality, very good MM phono stage and high end connections. As usual, it really depends on your taste, how and where you consume the music or sound and the room you use it in.