I have the Horizon 7700 and I did purchase the blue dot bobbin case, which I think, is the one you're talking about? The first couple of times I quilted, I completely forgot that I had the case and I had no problems with my quilting. I'd suggest, if you've been quilting ok with what you already have, there probably isn't the need to spend the money on the other case. I have used it since, but I can't say it made any big difference.
The main difference between that case and the one you would currently have in your machine is that the tension is set a little lower. You can achieve the same thing by loosening the tension in your current bobbin holder but, having the additional case means you don't have to fiddle with the tension on your 'good' case and therefore risk messing the tension up on that one.