Some keyboards sound better than others. What you want to do is start out with the best sounding keyboard you can afford. Usually, the more you spend, the better it will sound.
Anyways
You can make anything sound better, but what "better" means to you is subjective. Try recording through a DI into a good audio interface to get the best sound into the computer as possible. Then layer the tracks to make the sound not as cheap sounding. Process the tracks making them sound more alive. Mix and pan the tracks and before you know, the sounds will be so much more better than they were, regardless of the keyboard.
I know nothing about the keyboard you are using, so I'm not bashing it at all. BUT some of the keyboard brands spend a lot more time creating the pre sets making them sound great!
Its kind of like us as musicians trying to make the best quality sounding songs as possible and the process we take to achieve it. Some of the brands spend a lot of time trying to make their stock sounds sounds as great as possible, while many don't. But with quality, come higher prices in most cases.
My advice to you is to buy a keyboard that has awesome sounds already. Then make them sound even better! Why buy something with soso sounds to make them better sounding when you can start off with better and make them sound greater?
