In my experience, the lower end Monster stuff is great for the price. However, there are many more expensive power conditioners that are great for the price as well, and therefore significantly better than the Monster ones. I'd stick to what they call their "Stage 2" stuff, my experience has been that the higher stages limit current too much and unacceptably restrict dynamics. The only real suggestion I can give you is to try it in your system. Most power conditioners seem to improve some aspects of the sound and degrade others, so you really need to try them and make sure the improvements are important to you, and the degradations aren't an issue in the context of your system.
I don't have any experience with Blue Circle, so I won't comment on that, but I would recommend looking into Shunyata if they have a suitable product in your price range.
I don't have any experience with Blue Circle, so I won't comment on that, but I would recommend looking into Shunyata if they have a suitable product in your price range.