so i use a Avid mini mxbox interface with a MXL 990 condenser microphone to record onto pro tools 8 with m-audio studio pro 3 speakers. Now i get good sound from this set up when i'm done creating a track. but i want to take the mixing and sound quality to the next level. so i was wondering what i should upgrade to get better sound. should i get better monitors,microphones, mixer, better audio interface?...please help me out and give me some suggestions.

thank you