Tell you the truth, if you intend to do music in the computer, don't need to get expensive workstation. Now days software synthesizer is really good. If you really want a good workstation, i can sell to you mine

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Anyway, more important is your sound card.
If you are recording from your synth to computer or playing live, my usual practice is a little more than half (6/10). Then boost from the sound card of mixer. Then you will have a good quality of sound, at the same time rooms for you to do crescendo.
Otherwise, if you max out your keyboard, then the mixer will have to tone you down. Then you can't have your crescendo.
For Yellow Pika, I think Mid Valley have a few synthesizer for you to tried out. Personally, i think to be a pro, it will take some time. It takes time for your hand to learn new skills, and your mind to understand. It is like learning a new language. It takes time, practice and understanding.
Many teacher out there can teach or guide you to play music. But to be a pro, you need to be more than that. You need to have "soul" in your music - that's what my teacher said to me. The feel and touch makes all the different between an average musician and a pro musician.
If you are gifted in music, then you might be able to do it fast enough. But if you are not, then hard work and training will slowly build you up.
You need to first in love with the music before you can actually play it with all your soul.
In those jazz and pop classes, the hardest part to learn is the "feel".
Don't rush it, take your time to enjoy music.