Suntour offers an upgrade program, I assume you’re looking for an air fork? Raidon and Epicon forks are both air versions and available in lots of formats (I assume you’re bike has a QR and a straight steerer tube?)
For forks under $300 dollars I have found that both Rockshox and Manitou have great offers. Unfortunately, Rockshox’s selection of straight steerer forks has been shrinking. Your best bets from Rockshox are a 30 Gold Tk or an XC 3o. Manitou has many options that will suite any rider’s needs. If you go to their website, I’m sure you’ll find the perfect fork for you. Out of lack of experience with Manitou I cannot recommend one fork, but my experience with one of their old forks was a blast.
The TK Gold and XC 30 are good options. I have experience with both and they work well. Make sure to stick to an air fork. Those cheap Suntours don’t work well, IMO, and I don’t blame you for wanting to change!