DB651s with factory head unit -- recommendations for crossover setting on new sub

I upgraded the factory stereo in my wife's Mazda 3 with two pair of DB651s. I don't need loud, just clear, and with a little bass. Well, one out of two isn't bad. With a total lack of low end (but otherwise pretty satisfactory sound, I started researching low cost, low hassle solutions and came across the following:

Rockville RW10CA 10” 800 Watt Peak/200 Watt RMS Slim Powered/Active Sealed Car Subwoofer With Bass Remote

I think it's going to prove to be a good solution for my needs. Fits under the passenger seat, and it definitely gives some needed "thump" to the music. But now for the task of tuning the system for balanced sound. Any recommendations on where to set the crossover point on the sub? The shop set it at 60Hz, which I definitely think was too low -- I'm guessing around 110Hz? Or should I go all the way up to 150Hz? Ideally I'm looking for a clean, balanced sound on progressive jazz (George Benson/Joe Sample/Ramsey Lewis), with authoritative but not ridiculous boom on bass-heavy R&B and Hip Hop (think Erykah Badu).