thrice, welcome to the forum, good to see at least one other pentaxian in Utah.
I've heard good things about the Sigma, the DA*'s should be fantastic. But the I've
SEEN great shots taken with the kit lens. My personal opinion since you are new to DSLR photography would be to buy a lense or lenses in other focal lengths, before upgrading from the kit lense in that focal length... a 50-200, or a 14 prime, something to expand your focal length capabilities.
Learn to use the camera and kit lens well, and play with other focal lengths, you may find that you don't use some focal lengths as much as others, then buy the nicest lenses in the lengths you use the most.
Thats my $.02 and worth every cent you paid.
Most of all have fun!
//Edit: Thrice you posted while I was writing... sounds like you are at least looking at other focal lengths, thats good.