At one point, NAD offered a receiver, integrated and separates that were essentially the same amplifier and preamp sections. For example if you bought a 7240 recvr, it was a 2240 amp, 1240 preamp and a tuner all in one box. You could also get a 3240 integrated, that was the above sans tuner. You could argue pros and cons (separate power supplies, extra connections and cables needed, extra rack space required, etc...), but there should be little difference.
Where you would benefit is in the areas of expandability and flexible setups and upgrades.
I would suspect that either of the combinations would be an upgrade over your Pioneer.
