Thanks for those posts TKA, gonna have to read over that article now.
Basically, just accept it, Nukes aren't all powerful. If we assume that a Proton Torpedo has an average yield of ~10 megatons (Models vary from the Kiloton to Gigaton range, so I just took a number out of the air) and we know that it takes hundreds of proton torpedoes to take down the shields of the Lusankya. So, we can theorize that it takes the equivalent of 1000 megatons OR MORE to lower the shields of an SSD.
Anyway, here's a number for the raw energy used in the shields of the SSD:
Originally Posted by Wookiepedia
Its shields handled much of the power generated—an amount equivalent to the total power of a medium star (3.8 × 1026 W)
Give up, nothing produces that kind of power that we can develop and certainly not able to be made in the KotOR era. Your fantasy about a single nuke destroying it are just that, fantasy, within a fantasy.
@TKA: Bah, EU matters not
Edit: Reread TKA's points above Darth Jacen.