You would be better off to run 1gb DC rather than 1.5gb non DC.
General rules about Dual Channel:
Dual Channel is determined by your mobo, you cannot buy Dual Channel ram. But they do sell packs of dual channel ram that is designed to run in Dual Channel.
Dual Channel will only work if your mobo supports it. Also dual channel will only work if you have an even number of sticks. The stick(s) must be on their own channel.
On a motherboard you might have 2x blue slot and 2x red slots.
To run DC with 2 sticks, you need to have either the blue or red completely filled. To run DC with 4 sticks, just fill all of the slots.
Edit: all sticks need to be the same size. And the same manufacturer for a better chance of compatibility.
INTEL i7 930
3x2gb Corsair Dominators
EVGA GTX 480