In your price range, I would stick with stainless. You should be able to get a decent gauge stainless for that, unless you are going for something really wild.
Be sure to check Habitat For Humanities outlet store if you have one near you. I picked up a couple of very nice Koehler cast iron units for $35/each.
Other than that I’d say go with the stainless, and $30 worth of sound deadening sheet makes a huge difference in how nice an inexpensive sink sounds, and a bit of spray foam sure helps it hold the heat longer.
The OP didn't define his/her terms sufficiently to receive a meaningful answer. What are the prime directives?
1. Fit within the existing cut out?
2. Durability?
3. Style?
4. Choice of colors/finishes?
5. Single, double or 1/3-2/3?
6. In-stock-big-box or custom order
7. Since faucets were not specifically mentioned, it should be assumed the $300 budget allows for a wider choice of sink?
jack vines