Standing at the top of the 300 block of State Street, you have two choices for men's wear: The ubiquitous Gap and the local favorite Jazzman. One serves up a bland, predictable fare of polos and khaki while the other ventures into the a bit more adventurous territory (sometimes to a fault).
While your taste may vary, I highly recommend a stop into the Jazzman before venturing over to the lowest-common-denominator that is the Gap. Fully stocked with brands that are hard to find in the Midwest outside of Chicago, it's a great place to swing by to spruce up your wardrobe (casual or fancy-pants).
Also, the sales staff on Saturday dished out a compliment to the Yelp.com t-shirt I was sporting. Props to Mr. Ernst.