For the curious:
I currently have total forces of 1417/482 deployed against Pi Circax, one of Oldry's planets, that has a defense force of 1582/452.
I should be able to add 100-200 more attack each turn, and my planet's production is significantly more than his.
Based on where my fleets are now, I should have enough forces on hand to make my initial assault in about 3-4 days.