2x4's and plywood is all you need if your a handyman at all. First of all I don't know what your shooting or reloading plans are...one ore two calibers and a couple hundred rnds a year or many calibers and many hundreds of rnds.
If the former and you plan on only ever needing one press then your on the right track with 4-6 ft bench. if you ever plan on adding progressive press's in the future you will need 6-8 feet minimum. I have two progressives and a turret press on my bench, it is 8 ft long and getting crowded. If you have the room, build what you need now for later, for the extra $ 10 it will cost.
Because of moves, I have had to build a couple of of bench's. The one I have now is 8ft long and has 3 sets of x-braced 2x4 legs. Build the table top very sturdy, mine is a full layer of 2x6's with 3/4 ply on top of that, it's all covered with arbourite for ease of clean-up and removes any chance of slivers from the ply when wiping down.
A "fee-standing/ separate from the main bench" platform is best for your balance powder measure, it is essential if you plan on useing a digital scale.
Another small suggestion is to use screws in all the construction, nails will loosen up over time and pull apart with the stress of the press movement.
Lastly, if you can, anchor your bench to a sturdy wall with lag bolts (not one that has your wifes China on a shelf on the other side).