This is the first time I am considering these sorts of measurements. How would I know this? How would I know if the preamp in my AVR would clip, or if they are compatible with an external amp? Thanks for patience as I try to understand new information.
You know by searching out reviews that included bench test data. In my response to mtrot (post#44), I provided the link below, that I am repeating it to save you time.
http://www.audioholics.com/av-receiver-reviews/denon-avr-x5200w/measurements
Pay attention to the first paragraph in the measurements section, the reviewer Gene said:
"The AVR-X5200W has plenty of grunt via the preamp outputs to use in conjunction with virtually any separate amplifier should you desire more power. I measured unclipped output of 4.5Vrms from every channel. We like to see at least 2Vrms and the Denon met this with over 6db of margin to spare."
With 2V preamp output, I calculated that it can drive a power amp with 26 dB gain (that would be considered low) rated 200 W into 8 ohms. If you pair it with power amps that offer gains of 28 dB, 2V preout would be good for a 315 W into 8 ohm rated amp.
Based on a few Denon and Marantz AVRs measured by Gene, I expect their mid/upper mid range models will have more than high enough preout voltages for most if not all power amps discussed on this forum. So I would say you should have no worry about the following models, just as examples.
Marantz: SR5010, SR6010, SR7010 or newer/higher models.
Denon: AVR-X3200W, AVR-X3300W, AVR-X3400H, or newer/higher models.
I would also take an educated guess that the following Yamaha AVRs can do the same.
RX-A1030, RX-A2030, RX-A3030 or newer/higher models.
You can spend a lot more money on higher end separate prepro or preamps, and you still have to find out if their preout voltages are higher enough, there is no short cut. Some high end components do provide more detailed specs, and if you think you can trust their published specs, then you don't have to search out the bench test results for them.