Hopefully we can help you out here as you must be as frustrated as hell.
When I get a new receiver I typically connect the Fronts only first and try a decent stereo sound source. Then add the Sub. I suggest you start like that. The Denon 3500 should have more than enough power to light up your speakers.
Your B&W DM603 S3 loudspeaker Specifications:
"2½"-way vented-box loudspeaker. Drive-units: 1" (25mm) aluminum-dome tweeter, 6.5" (165mm) woven-Kevlar cone bass/midrange, 6.5" (165mm) aluminum-cone woofer. Crossover frequencies: 150Hz, 4kHz. Frequency response: 44Hz–22kHz, ±3dB on reference axis. Frequency range: –6dB at 34Hz and 42kHz. Dispersion within 2dB of response on reference axis: over 40° arc horizontal, over 10° arc vertical. Sensitivity: 90dB/2.83V/m. Impedance: 8 ohms nominal, 3 ohms minimum. Power handling: 25–150W into 8 ohms on unclipped program. Harmonic distortion: second and third harmonics, <1%, 55Hz–20kHz (90dB SPL, 1m). Maximum recommended cable impedance: 0.1 ohm.