@sns - I'm afraid it's YOU who are incorrect. lanx00003 is correct. I owned an A8, and it DOES have a 'proper' analogue volume control circuit, and it's VERY good. I tried it direct into my Threshold S300, bypassing my Audio Research Reference 3, and it was almost as good, which was a great surprise. It was so good that I thought that the pre-amp in the (twice the price) A10 must be better, so I thought I may be able to ditch the Ref3 with a purchase of the beautiful (IMO) A10, so I bought one. It's still not as good overall as the Ref3, so it's staying.
dmann777 - You could try the A8 direct into your power-amp, but it would depend on how many sources you need to switch, to determine if that's an option for you.
You must set your A8 to volume pass through, so you are not using the pre inside it, as, if you do, you are now using TWO pre-amps in line with each other! = not a good idea. So set the A8 volume at 100% and deal with other issues. Maybe the -3db thing, which is easily implemented in the A8, will help, but using RCA may be the answer to reduce possibly overdriving your pre. There is, generally speaking, no sonic advantage to using XLR unless you need to use very long cables.