Hope you don't mind me jumping in here.
You could also try this with your SPL (if you have one). I have a Yamaha RX663 so I am not familar with Audessy. But I have 3 subs and this has worked for me using an SPL meter and the tones from the receiver.
Run Audessy with only one sub on. Adjust the level of the sub at the sub. Turn it off. Turn the other sub on and run through the process again. Keep in mind that if each sub is at say 71db that combined you will get a higher reading (around 3 to 5 db more).
It's a easy way to get them balanced between each other. Don't forget to set your reference level for the test tones. I set mine at 75db.
I am currently going through the process of installing a BFD1124P. It is a challange to say the least. I have heard it on a couple of friends setups and it is amazing. I hope to have mine up and running tomorrow night. I have been working at it the last 2 nights.
The BFD 1124P, midi cable, and 1/4 to RCA cables cost me about $180.00.
I am by no means an expert on this stuff, but I sure enjoy it! This is something that has worked for me. I am sure you will get many opinions and views.
Good luck and let me know if I can answer any questions.