Every review I have read of the Turbo Boost says it really is only faster with older slower processors. Sounds like that has not been your experience? Alot of the user reviews I have read complain about software bugginess and poor quality results in some cases. I've always been interested in the device but those things have kept me away.
The elgato Turbo.264 HD dongle is hardware encoder for MP4 encoding. Using it will cut your encoding time down drastically. I'm using 1.1.4 software but elgato products especially this dongle has its fair share of audio sync problems - I haven't tested the 1.1.4 extensively but I used the old 1.03 version and was all good.
It can encode up to 30Mb/s bitrate.