I'm not a big fan of mixing and matching ram types and brands but theoretically theres nothing wrong with it. It can on occasion cause stability issues, in particular when utilizing all memory slots. Unless your believe you'll actually use 3gb of memory I'd personally be inclined to sell the Corsair stuff and just use the 2gb of Super Talent.
Dual channel can be a tricky beast on occasion, and sometimes behaves perfectly. Traditionally dual channel requires to identical matched DIMM's to work properly but will generally work ok if the DIMMs are similar e.g your 2 sticks of Corsair. In order to get dual channel working with your setup but the 2 sticks of Super Talent on different channels and the 2 sticks of Corsair on different channels.