Dropbox replacement?

I ran out of 50Gb limit on dropbox and am not sure I want to go to the next level (100Gb), it is a) too expensive and b) I will overgrow it in 6 month or so c) data doesn't really need to be in the cloud but it needs to be synced up between few computers.

Is there an alternative to dropbox? I don't mind paying but something more reasonable than dropbox rates