Basement support question.....
I woudln't use 4x4s, that's for sure...6x6s would probably work, but don't go by what I say with that, they may be too small too. Unfortunately you haven't provided enough information to answer your question. I would call a struct engineer and have him size them for you. This can be done very cheaply, I'd imagine you can get one to do the simple calcs for a couple of hundred bucks.
But to answer your question, they would need to know the total span of the beam, the peremeter dimensions of your house, how many floors it is, etc. They don't have to do drawings or anything, just write a simple letter and provide you with a detail or two...it would be worth the investment in my opinion.