When you use the pre-outs of the receiver into the amp, and this is the ONLY way to connect these two devices, you will be by passing the amplifier section of the receiver. The end result is likely to be the same if you do this as it would be if you used the receiver as a stand alone device. I would do some heavy duty comparisons and return the amp if I could.
My opinion then would be to return the receiver. Buy a dedicated pre amp for the power amp.
The Nakamichi receivers were somewhat bogus about their design and implementation of the Stasis amplifier concept and the Stasis amplifier concept was the only thing that was really noteworthy about the Nakamichi receivers. In other words, the Nak receivers just weren't anything to write home about. There were far worse receivers on the market back in the mid '80's but the Naks were just about average when compared to the competition which at the time was top o' the line Yamaha, Denon and Luxman all of which were building less successful products than they had just a few years prior. Using the Nak receiver as a pre amp only, you would have done better with a stand alone pre amp doing the job IMO.
The Nakamichi Stasis amplifiers were not too bad, they lived up to the design goals Nelson Pass set forward for the Stasis concept and they did what a decent power amplifier should do. They were not standouts by any stretch - they did not sound like the similarly powered Threshold amplifiers using the Stasis designs - and they did not do much for Nakamichi's reputation but they were not absolute abominations either. Be careful with your speakers selection with the Stasis amplifiers and you'll have respectable results considering the age of the gear.
hi its worth a shot connect the power amp into the preouts on the reciever then it would bypass the front 2 amp section on the reciever,,, therefore the reciever will be a pre ampfor frnt 2. since it has its own power supply it may sound better then the reciever on its own its worth a shot.