Amp/Pre-amp Bridge 101

I'm in need of some very basic assistance to help my dad get his 2-channel audio system running. He's got a NAD 701 receiver and recently purchased a used NAD 2150 power amp. He asked me if it's possible to utilize the 701 as a pre-amp but also to take advantage of it's 25wpc power to use in conjunction with the 50wpc from the power amp. On the receiver, there are pre-outs (left and right) and a main-in (left and right) both currently linked w/ the metal posts. The amp simply has mains (left and right). Anyone have a suggestion as to whether or not this idea will fly?

Thank you kindly,
No, the power of the two units cannot be combined. Remove
the jumpers from the 701 and use the "pre-outs" to
the "inputs" on the 2150, amp. Hook speakers to
the 2150 amp.

He could "Y" out of the preamp outputs and come
back into the receiver, but it still won't combine the two
amps. This would let him run an additional pair of speakers
from the receiver.
The only way that I can possibly see utilizing both amps is to "Y" out of the pre amp outs. One end goes to the 2150 and the other into the 701. If you have a away to adjust the levels on the 2150, you can bi amp your speakers, assuming that they have this capability.

Otherwise, just choose which amp sounds better. mentioned above, you can run two sets of speakers.
I'd say use the receiver as a preamp into the power amp...and use a good pair of cables. This will provide the cleanest sound. Don't start messing with y-cables of questionable quality.
Go with the purest signal.