Mikrotik RouterOS (Score 2, Interesting)

Simplest, quickest way to do it, and does everything you're looking to do.

They put a relatively decent shell interface on top of linux that hides a lot of the complexity, and also have a good GUI management utility (I don't use it myself, but it can do everything the shell can).

It'll run on most hardware, including x86. You'd have to buy a license, $45, but it's worth the time saved figuring out how to get all the different parts tied in together.

And there is an active community forum with helpful people in case you run in to trouble.