To get the most from a dac what is required input?

Yes it upsamples to 192

I wouldn't angst about transports much unless you have a high resolution system that is highly optimized.

The easiest way to improve your transport is to move from a platter based unit to a hard drive transport. This will neutralize the jitter difference between transports by largely eliminating it.

And there are a whole bunch of other benefits which will lead to an increased appreciation of your CD collection and generally much more listening.

Jitter output is one variable in transports that can make a sonic difference. As to how much jitter the Krell puts out, who knows. Another transport, dedicated or not, could be better or worse.

Another variable is what digital out/in your transport/DAC is optimized for. For example my Proceed transport is optimized for AES/EBU output, my DAC optimized for I2S input, I should attain maximum sonic quality using a transport optimized for I2S with my DAC, or I could get a DAC optimized for IES/EBU.