That is a really nice looking set up. Like you, I just moved up to the A-21+, what an amplifier! The Rogue audio is a nice looking piece! I just like those silver and champagne components!
I just keep both pots at minimum, full counter clock wise. I am using the Parasound JC-2 BP pre-amp. You can put them really anywhere you like.
I was also curious where to leave the gain controls on the back of the JC5. I emailed Parasound and this is the response i got. For full context, i use the Parasound Jc2 and my speakers are JBL 4367. For me, leaving the gain control at maximum resulted in the volume control ramping up ridiculously too fast. I choose to leave the gain control on the back of the JC5 in the middle setting. So this is their response : 9 times out of 10 the amp's gain controls will be set to their maximum. But if you find that the volume control on the JC2 ramps up to fast you may want to turn down the amp's level controls as you have done. There is nothing wrong with leaving them where you have set them. The only tricky part is making sure you have turned the Left and Right the same amount.
Just so you know, in regard to adjusting your amps input pots, there is a way you can perfectly balance your R&L speakers, where you will know, without a doubt they are perfectly balanced. Because they are in the same place does not necessarily mean they are exact, but you can know by connecting a Hafler speaker to the hot leads on the amp, and adjust the balance knobs until you reach "exact" center channel information and you then know you are completely balanced.
