I don't think there would be an issue. They are really twins, with the 600 reaching one or two hz below and a 3db more output. How many seats do you have? And BTW, it is more likely that you will get better bass from the side or the back. The front is often too crowded.

As an example, I finally moved my 500 behind my couch. Perfect musical bass (the most important for me; cellos and double-bass sound just amazing) and it acts as "bass shakers" when T-rex decides to make a run for a jeep!

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