Well then I say go for it, but I would like you to know that the 4500 has a theoretical advantage. That is, you can set it to run 7.1.4 and assign the front left and right channel to pre out. In doing so, regardless of how many speakers you actually connect, you will have the front left and front right preamp output disconnected from the corresponding power amp channels input. That would make no difference for you if you don't connect the preamp outputs to external power amps. If you do plan on using an external power amp, especially one that is rated much higher than 200 W, then it may, or still may not matter as it also depends on other factors.
Now you can make your informed decision.