Okay, fellas, so to summarize the thread (before it goes off the proverbial track of increasingly technical jargin)...
No discernable performance (i.e. perceived power) increases can be verified by doing this "passive bi-amping" which, one more time, I was referring to was:
Taking the "back surround" channels of my AVR and using them in conjunction with the main front channels of the receiver in order to feed the two terminals on my bi-ampable Polk RTi12s...
...correct? I wouldn't perceive the mains as being "louder, punchier" or otherwise "better powered" in any way, would I?
One of the main benefit of bi-amping comes from isolation of the two parts of the system: woofer and tweeter. If you look at music spectrum you see that low frequencies are far louder than highs. So the part that forces the amp to max out is the low frequencies. When amp distorts due to its inability to have clean power at that listening level, it creates distortion that is at higher frequencies which normally are reproduced by the tweeter. If you have two amps and have each one of the independently drive the woofer and tweeter, that extra distortion no longer makes it to the tweeter. So you get cleaner sound. And it will be "better powered."
Now the power gain may just be 10% so we go from 100 watts to 100+10 watts (100 for woofer and 10 for the tweeter). That is OK. We don't need to go to 200 watts to have a benefit. There is a flippant comment made that this benefit won't be there ("current limiting is not common"). But no data is provided to back that and in the other long complicated thread, I showed how that argument can be false.
So the issue here is not the theory. The theory is helpful. What you need to determine is if your amp is operating near its limit. If it is not, then you should stay with your current setup. The way to determine that is to play music with very high dynamics. I like drums. Then turn up the volume and keep going up even to uncomfortable levels. Do you notice a change in the quality of the sound? If so, repeat this a few times with your eyes closed and see if you arrive at roughly the same volume level. If you do, then you have likely hit the limits of your amp and it is worthwhile to add the second amp and try the same experiment. If there is no improvement, then you can stay with this or go back to single amp.