Rodney, there's little need to be concerned about any performance specs of modern receivers when they're being used as pre-pros. The output impedance, which was mentioned on the other board, is typically a suitable value(e.g., about 100 to 500 ohms)and unless the gain of the separate amp is unusually low(e.g. less than 25dB), the output from the pre-outs is typically plenty to drive it to full output.
What are relevant factors are the features that you want in a receiver/pre-pro, beginning of course with a full set of pre-outs.
