Thanks for the responses guys.
Running them together is a bit smoother in the room, but the two together actually play at lower SPLs (5-8db) because of the impedance issues on the 600.
The blue line is the EP600 by itself, the purple line is the two running together with the gain on both nearly maxed out to overcome the impedance issues on the 600.
Overall SPLs are lower and room response is a bit smoother...
Jakewash, I'm thinking about trading down for something that works better paired up with another sub. I've definitely burned all of my speaker "play time" this weekend in my wife's eyes, but I'll try any other solutions you guys have the next time I get the chance.
