if you're doing a new build from scratch, then the ps360 vanilla is the way to go, or you can get the paewang revolution which works just as good for a dual mod straight out of the box
if you want to do something more complex and custom like PS1/2 and dreamcast support as well as PS3, Mcthulhu is the way to go. You'd have to get another board inside the cthulhu if you want to use it on an xbox though
it'd also depend on what systems you'd want it for