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

540c or 640c are very good for the money not sure about the 840, if it does not have the superb wolfson DAC might be best to avoid it.

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.