I'm under the impression he would also be losing some additional low frequenecy management--9-step subwoofer crossover selection--by going with the rx z1. And considering a $1000 increase in the price tag it might be in ones best interest to settle for the 2400 and pick a nice external amp in the near future if he is not happy with the performance of the 2400's internal amplifiers.
Gene, do you know if Yamaha has any plan to release a mid-priced receiver in the near future? i.e something to fall inbetween the 2400 and the Z9--we'll say a z1 with a few of the rx v2400's features.