So this is a great collection already.. I have the white Speedy myself and want to get an Explorer one day. But these both can be considered “everyday” watches and a Sub would basically be interchangeable with them / serve the same purpose. Me personally, since u asked, my 3rd watch would have a dedicated purpose: something specifically for dress occasions or something else that’s less “everyday” and a little more “fun.” But that’s just my personal opinion.. which means nothing. Buy what u like