I am not the server owner just help with missions a bit and being a communications guy
As far as I know R1 runs Quad @2.5 and 4 or 8 GB RAM. 4 should be enough as server do not use much RAM. I would recommend a processor with higher clocks, the more you can afford the better because the game sometimes has problems when the 1st core is 100% utilized.
Do not know about traffic. BigRepa told once it is not as bad as reported back in March by some server owners.
R2 and R3 run on virtual PCs.