Need upgrade, sell the B&W 602 and get a tube amp?

Focus on the amplification more than the speakers. If you borrow a better amp to try, you will find those B&W sound better than you think. If you're using cheap cables and wires, replace them also.

If you listen to music more that watch movies, sell the Denon and get a Rogue Tempest Magnum Integrated. The 602's are good speakers for a fair size room. Also, what is your source?

The source: Panasonic 91- nice unit with separate outs for music audio. Using OK connects and 12ga stranded speaker wire.

Look into a mellow/smooth interconnect.(Van den Hul D-102 III.) Also, if the 2802 has metal jumpers from pre to main in, consider replacing those also w/VDH. Will tame the harshness. Also, find a "Straightwire" retailer. Try out some Quartet spk. wire. They would probably loan you a set
to try out. Excellent wire at a very affordable price. If that doesn't do it, consider a spk. or amplification change.
IMHO, I don't think you'll go wrong with the VDH interconnects and you can most likely try out the spk. wire
on a loaner basis. Hope things work out. Bill