I agree with those who advised to keep your current setting. It is more interesting than the halo, and the halo looks kinda' generic. Your current setting is beautiful!
Its a little over a carat, but I actually think it may look somewhat bigger than that...
My current stone is a cushion, and I would be upgrading to a bigger cushion.
How attached to the diamond are you? If its doing your head in and want a bigger diamond, go for it! Not everyone sees the diamond as something you need to keep forever. But if you're too sentimental with the current one and all you want is more finger coverage, halo it.