I would like to know if the "common mode rejection" used in the 7500 makes it a better amp than the 7200 in terms of sound quality. I bought the 7200 during last month's sale. I have it set up in a 5.1 setup and it is a much improvement over using a receiver. (so two channels remain unused).

As I read more about the Outlaw amps I am a bit concerned I did not purchase the 7500 for the same price. People have stated there is audible improvements using the "common mode rejection" amps (7700 & 7500) over "single-ended designs" (7200 & 7125). Baring any unforeseeable events I plan to use the amp for a long time. My question is should I send the 7200 for a 7500 while I am still within the return window or just keep the 7200. Thanks

Edit.. I do not care about the XLR connectors since my preprocessor is right next to the amp

To take full advantage of the 7500 you'd have to use the XLR connections. You'd still get some improvement in slew rate but the CMRR depends on using the XLR inputs to cancel noise that is common on both the positive and negative inputs.

If you're set on single ended then I think I would stay with the 7200.

EEman is 100% correct that the key to common mode rejection ratio is having balanced input signal to feed the amplifier, but it is important to realize that the XLR connector itself is more a result of a need to ensure a balanced signal is presented to the amp from the pre-processor/other input devices -- the most common places to find XLR connectors and even balanced 1/4" plugs or jacks is with sound reinforcement amplifiers / musical instruments: http://www.musiciansfriend.com/resources/article/Balanced-Vs.-Unbalanced-I-O--Whats-the-Deal/m710696 http://www.sweetwater.com/insync/common-mode-rejection/

From a technical standpoint induced cable noise is also a problem that folks in the telephone and data world also have long dealt with: http://www.maximintegrated.com/app-notes/index.mvp/id/2045

As to the OP's question about "sound quality" there are legitimate reason to consider how a balanced amplifier is operating vs a single ended design with more than a few folks that believe a simpler unbalanced design is actually a better value...

If you're happy with the sound you have, I'd just keep the 7200.

Not only are you not hassling with all of the exchanging and shipping issues, but you keep two spare channels. These could be used for any number of applications you may discover such as if you decide to upgrade to a 6.1 or 7.1 setup, as a second zone pair, or even bi-amping your mains if you need (want) to do so one day.

Plus, all the stuff those guys said up above me.

I have a 7125 and a 7500 amp and there is no discernible difference in the sound quality between the two. The XLR connections allow for longer runs of cable without interference and they provide about 3 db more headroom for difficult to drive speakers. The 7125 is very similar design to the 7200 and I would keep the system as is if you are happy with the sound right now. Plus as stated above you have two extra channels to use as needed.

Thank you guys for your input. @EEman, I just checked from the manuals and the 7500 and 7200 are listed as 50 Volts/microsecond slew rate. Since I plan to use it in a home theater setting the XLR does not provide much added benefits. I really like the suggestion by Owl's_warder. I am going to use the remaining channels to power my second zone. Awesome amp!!!

7500 and you will never need an upgrade. Totally flexible and powerful.