If my payoff on my house is $92500 how much more to pay off in 15 years?

Read the question thoroughly! I was going to refinance my house and i still might but heres the deal i currently owe $95200 and my monthly payment is 736 per month, my interest rate is 8%, ive been in my house for 7.5 years and my credit score is 643, i havent been late in the last 2 years. My house appraised 2 years ago for $109000. My mortgage company said if i paid closing cost of $3000 they could refinance my conventional loan for 15 years for $681 per month or no money down for an fha loan with a 15 year loan and $749 per month. What is the best option and could i accomplish the same thing by paying a lil extra per month? If so how much extra?