There is something you should know about published GMAT scores. The upper end of the published range for each school is set by kids from India who spend one to two years studying for the test. You don't have to have the highest score on the test to get in, but you do want to be at or above the median to increase your odds.
Secondly, the best thing you can do to help your case is to differentiate yourself with your essays. In admissions, similar applicants are grouped together. The foreign engineers are evaluated against other foreign engineers. The US engineers are evaluated against each other, etc. You either have to be near the top of your specific subgroup, or be so unique that you can't be grouped with any other applicants.
From what you've posted on here, I assume that you will be the only 38 year old accountant applying to most b-schools. Because of that, you can probably get into Rice with a 650 and a compelling story of what you want to do afterward.
