Why is your score that low? Did it explain the reasons? No debt, no late payments? Do you have way too many credit cards that you don't use (or use, it doesn't matter)? Damn..
Mine was 800 (795 actually, but 800 sounds so much better. damnit!) a few months ago but I fixed a couple of things on there and it should have went up. $20 medical bill that I didn't even owe was in collections. wtf? Check your stuff! I have to go back and check now to see if it changed.
I would just put a larger down payment on the house. I think that is favorable to a lower rate. The pros can answer that one.
Either way, interest rates have been somewhat climbing to 6.5% area recently. Not too long ago they were 5.5% or even lower. Fucking Mexicans.