Cambridge 840c or Pioneer PD-65/Benchmark DAC 1

Neither, get a used Bel Canto DAC2 for your PD-65. If you want a real bargain try the Keces dac sold here for $350 with the opamp upgrade.

Seems that you can't find anyone that has experience with both. I haven't heard the Benchmark, but had a Bel Canto DAC1 a couple of years ago and was not impressed.(even though I like Bel Canto in general) I have owned the 840 for about a year and find it to be excellent, more like a $2-3k player.
I believe that it actually has 2 of the Wolfson dac's, one for each channel.
I use it w/ a tube amp and it is transparent, detailed and musical. Not certain that it would mate as well w/ a SS amp that leans toward brightness. If you buy used, I would imagine that either the 840 or the Benchmark could be resold w/ no problem.

The 840 uses the Analog Devises Dacs, 1 per channel.

Sorry about that, Phill has it right, according to the Cambridge site;
Dual differential DAC configuration using high-end Analog Devices AD1955 DACs

But it is avery good player.

Anagram Technologies