cheap and reliable payment gatway?

[Twinkie]

I am planning out a web site for a custom computer building business for the first time, and I never thought about how to pay online. After some research, I checked out authorize.net, and the penny pinching was horrible! Fees here, Fees there...

I plan to integrate the form into my own web site (AIM I believe), and I need some sort of fraud prevention services, but for the cheapest possible. What is your recommendation on a cheap, reliable, and anti-fraudulent payment gateway?