I called a couple times asking about this and was told the answer is NO. If using the dining plan, you can only get category 2 or 3 seating. I asked if I could pay the difference (only $5 or $7) and was told no.
Please complain. I did. This is another example of treating dining plan users differently and poorly in comparison to people not on the dining plan.
I'm paying a lot extra for the "Deluxe" dining plan but still cannot get category 1 unless I pay for the whole meal with a credit card.
If I have to, I'll do that, but then, we will have to find 2 more table service meals to eat -- and well, I don't want to spend all my time at Disney eating and getting fat!