For my mind the next step up from the Sunbeam would be the Iberital Challenge. A number of the site sponsors sell them so would be best to pm them to get an idea of the price. I bought mine when I bought my machine so wont hazard a guess. There are reviews on the Iberital in other threads which also discuss other grinders as well. So well worth a search.
Depends on what you intend to use the grinder for though as well. French press? Espresso? Both?
That will see you get better advice and maybe also your intended budget. Generally it is better to buy the best grinder you can as it will most likely serve your purposes as you upgrade brewing equipment.