Proceed AVP sub output and output connections questions

I know its old. using it for a 2.1 system.  I have tested 2 amps and get the similar results.   power is about same for each amp. one class D one is AB>   I read output on the RCA is max 5 volts.  XLR max is 10.

with the levels set max it seems I dont get the bass as soon as I thought. its like at 3/4 before its hitting good.  I just dont know if that is normal. 

now looking at the XLR 10votls out I was wondering if I can use the XLR outs and the RCA outs at the same time.  I have a sub amp to hook up and its currently getting signal from the SUB out.  if I were to use another output I would loose the sub control on the front panel.

the class D amp needs a bit of voltage to reach output.  I thought the proceed @ 5 volts would be enough
RCA output is already 6db lower than XLR, so if you are using XLR outputs for your left/right channels, the subwoofer needs to be adjusted at least +6db.  If the bass is still not loud enough in relation and you are using an external amplifier for the subwoofer, it could be that the subwoofer driver is very inefficient (when compared to your main speakers).  I would maybe look at a powered sub where you can adjust the gain up higher.
I have the output for the main speakers using the RCA outputs. I am using the S for sub output to the amp that powers the sub.  the amp has adjustable gain on it. 

but I am afraid if I use the XLR output it will no longer be controlled by the sub adjustment on the front panel of the PRoceed AVP.  

I guess I will try it and see. I fugured a AVP user would know what I am talking about.