Mimberman has it right IMHO. Going into a preamp or integrated, the only case in which I would choose to lower the computer's (or the DAC's) output level at all would be if the final output from the DAC were too much for the amp or preamp's input.
Here's how I would check. Set your computer to max output, your DAC to the same, then see how much travel you have on the YBA's volume control before it gets too loud. If you are up to 11 or 12 o'clock before the too-much point, you're probably OK. If you only get to 9:00 or less, you should reduce the input level.
If you want a measurement to back this up, go to your YBA's spec sheet. Find out the YBA's maximum input level for full output. If it's less than 3 volts (that's your DAC's max output level), reduce the MD-10's output level till it matches the YBA's input, but keep your computer's output at max.
You may have to ask a technician to tell you what setting on the MD-10's analog outputs corresponds to your YBA's input.