Hi - whilst we don't really dive computer decompression, if you do decide to go down the DIR route later the Vytec is a good purchase to make as it will run in gauge mode (we bend computers

).
I see you have done TDI Avanced Nitrox and am sure that they taught you how to use tables. Why not dive these - and if you want a computer as a 'back up reality check' then the Vytec is as good a place to start as any - and cheaper :D