You can still get Breakaway Live, and then you’ll be able to run up to 4 stereo-independant audio engines with low latency. But you’ll have to pay for two cores in your case (something like $200).
You’ll need Breakaway Live, correct. Breakaway Home Theater ("BHT") is a 5.1 core. Just because it has more channels, doesn’t mean that anything is independent. You won’t be able to do that with BHT, you need Live.