I'm thinking of buying the license One Time Branded (125$) but later want to upgrade to a One Time No Branding license (374$) but then I have to buy this license or can I upgrade only paying a little more?
I hope to help me as soon as possible.
Thanks.

I think you can pay the difference later on for brand free but I'm not 100% sure...

You can verify this if possible?
Otherwise I just bought the last license.
Thanks.

Only way to confirm 100% would be to try to contact xam and ask him.