bro one good suggestion from me ( at least i think this is good suggestion) while searching for universities please don't forget to read the profile of faculties and carefully look over their research programs. if you find any professor with good research program with sufficient fund and also find that research program is of your interest, write professor about your interest and write him that you want to work with him. You need to get less GRE score to get RA position than TA position no matter which university you are going to apply. I have seen that some universities will never offer TA position to international students and moreover TA job is hectic job. You will simply kill your time that you need for your study. So try to get RA position.