At one time I was looking at getting the JDS Labs C5, but I decided to get the C&C BH instead, and so far I have been very happy. I was wondering the exact same thing as you were (if the cost-to-performance ratio was worth the extra money for the C5), and from the research that I did, it was very subjective. Some people still seemed to like the C&C BH better, while others felt that the C5 was better. The biggest game-changer for me was the battery life. 50+ hours (C&C BH) vs. 10 hours (C5), pretty much sealed the deal and steered me towards the C&C BH.
Here is a quick review from miceblue425 where he compares the C&C BH to some other amps, including the O2 that you are looking to purchase. Hope this helps.