Well, most feats are of the raise the DC and CL of acid spell variety. I also have precise spellcasting (the one where you can miss one guy in an area) and empower.
Since we pseudo fast-forwared the rest of the campaign I just ended up going with straight sorcerer in the interests of keeping it simple.
I did pick up a ring of x-ray vision, to sort of duplicate seeing through rock. Its not perfect but it does the trick. I haven't used it yet, still having fun with Polymorph Any Object. Green slime is my current favorite thing to polymorph stuff into.
DS