Matt was talking about RCA to XLR connections in the case of a pro-amp....this is a unbalanced (from you AVR) to balanced (to a pro amp) connection. Very few pro amps will have rca connections on the rear but there are some that do---none the less ordering, these cables is easy and relatively inexpensive as Matt pointed out...
So it is very possible to easily hook up a pro amp to your Denon with unbalanced pre-amp outputs. That aside, as long as you level match all your channels you will have no issues...Also your 3808ci is rated at 130 watts a channel not 140---thats the 4308ci....