True RC sells a balancer that works with up to 6s. It's the E-Station PB6, and can be found on the chargers page of their website:
http://home.comcast.net/~truerc/Charge/chargers.htm
Are you planning on balancing both 3s packs on one balancer? If you are, you might need to make an adapter harness like I showed in a couple of other threads.
It looks like the PB6 uses the Hyperion/Polyquest taps (balancing connector), which is what Maxamps uses standard on their batteries.
SH Z-Car, Custom Crawler, 8s Savage,
12s XTM XLB 1/7 buggy,
4wd 4-link rear/IFS Pro4 truck,
Custom Hyper 10 Short Course,
Belt-Drive Mammoth ST 1/8 truggy, 4s 17.5 MM Pro HPI Blitz