Hard question to answer. The question to ask is here is the first instance where you feel there is a lack of quality? If you think about it your original question will be easier to answer if you can identify where you think you could improve through out the recording process starting from tracking, to editing, to mixing, to finally mastering. We as the reader don't know what the quality of your raw tracks are. I am not familiar with your work so forgive me if this seems rudimentary but a safe way to check could be in this order: 1. Quality of the instruments, 2. Quality of your mics and/or DI's 3. quality of your interface and gain structure (meaning not clipping going into your software), 4. editing (including tuning and quantizing), 5. Mixing, 6. and then mastering.
Please add on if i missed anything.