You are right on point with my question. I do have another receiver, which is a good idea. However, I prefer to toggle the speaker inputs with my existing receiver using the menu settings. I think this will be easier than plugging and unplugging repeatedly. What I am wondering is that if I plug in the second pair into the front presence speaker input, will they sound differently than if I plug them into the regular front speaker inputs.
I am confused! The beauty of using two receivers is once you initially set things up, you do not have to do any plugging and unplugging! If the same RC will work on both receivers, the switch between speakers is instant! If they are two different brands or otherwise not on the same frequency, it takes about a second (there is interference if you attempt to press both mute buttons at the same time, so you have to do it sequentially). But you can level match things very easily and it affords a very good platform for comparison while being much more convenient that changing speakers assignments and then having to adjust the volume.
I am assuming that you have a source with more than one output. The DVD/BD (&CD) players I have all have at least HDMI, optical, and RCA outputs, so you can feed the same signal to both receivers at the same time. Alternately, you can use the "Tape Output" or "CD-R Output" to go from one receiver to the other.
If you own a second receiver, that is how you should do this unless the second receiver is a total piece of junk! Just be sure all settings are pure direct without any EQ.
If you have any qualms about differences between receivers affecting the sound, go ahead and do the comparison and after you have a good sense of the differences, you can swap the receiver-speaker connections so the speakers are now associated with the other receiver from your previous trial. I'll bet on differences between the speakers far, far outweighing any differences between receivers, DAC's, circuitry, etc!