well first off you do not need kegs. 2 10 gallon beverage coolers will work fine.
You will need a kettle but I think this will be easier to find. You can either snag a keg or get a cheap aluminum kettle from a restaurant supplier.
I personally would go electric herms. Easy to implement all you need is some 3/8 copper coil and a hotwater tank element. Run a PID which is 40 bucks get a pump and your set very little work. Also you will need a ss relay other then that its very simple to use and make.
Rims you have to worry about burning an element out and your going to need expensive fittings to install the heater in. Most guys use SS but copper is les expensive but still the fittings get pricy.