Hello Tan-There is an mp3 mixing clinic where people can get there mixes listened to, you might want to post this there. I listened to the clip and even though its out of my genre and short, it sounded lacking in the bass, i expected my sub to be rumbling but it didn't budge. My suggestion would be to check this mp3 mix against your studio monitors to see if your bass is translating correctly and adjust your listening environment accordingly. If they sound close to identical i would say you're getting the sound you want and there's no reason to refer to your mix as amateurish. The level could certainly come up, see what your highest peak is and increase the whole track to make the highest point right near 0 is another suggestion.