I echo Vivek's sentiments. Please decide based on your budget. Since you have mentioned that your firm is a startup, it would be best if you don't try to compete in terms of pay.
If you still wish to do so, please consider purchasing a salary report from Kelly Services or any other top HR consultancy. This would provide you with quantified data that you can reference, rather than collecting it randomly.
While any job site can provide information on pay for similar positions that you are hiring for, your hiring consultants can also easily share what your competitors are paying. However, this may not be the most trusted source of information.
As you revise the salaries, identify how you plan to enhance each role. Assuming you have strong measures in place, could you consider implementing pay-for-performance strictly, along with the basic and other components?
I look forward to hearing from you.