I always recommend folks purchase gifts from the couple's wedding registry. People register for a reason...they are items they need or want.
Perhaps you can add to a registry gift to make it unique. If they registered for a crock pot, buy the crock pot, a slow cooker recipe book, and maybe purchase a set of cooking utensils from their registry or stainless tongs, or bundle it with a set of nice kitchen towels, etc. With your budget, you can purchase several medium to small priced gifts and make a nice little theme.
Most couples don't appreciate gifts that weren't on their registry, myself included. We had registered for specific bath towels, and got them, but someone also gave us a pair of random towels. We also got a set of hors d'oeuvres knives that we didn't register for and never used. There were a few other random things also. The only item we received that was not on our registry was a beautiful serving platter (white) and I do love it. If it were any other color, I wouldn't have used it. All of our dinnerware and serving bowls/platters are white.