Better than premium

Solution 1:

Neither "premium" nor "deluxe" has a precise meaning (unsurprising, since they are both words in advertiserese, where precise meanings are undesirable because somebody might try and hold you to them), so there is no answer either to what order they come in, or to what you can put between them.

Solution 2:

Colin is absolutely correct that "premium" doesn't really have a precise meaning. It is used in marketing to imply a somewhat better than baseline quality. There are loads of other such words, but which actually means a better product than which others is almost entirely up to the company's marketing department.

Some examples:

• Executive
• Platinum
• Gold
• Diamond

And of course "plus" added onto any of the above to knock it up another notch.

I think the only thing I've seen that definitively means "best" is "Ultimate". I wouldn't put it past a marketing guy to invent "Ultimate plus" though...