I5 2300 @2,8-3,1Ghz quad, 16gb ram, 2x1tb HDD, 100Mbit line. Hosted in data center.
Ok guys, chill out. So even for a small server (15-20 slots) you need atleast a dual core and 2 gigs of ram, RIGHT?
RAM is almost "free" today, why be cheap on that? If you run 32 bit OS, go for 3 gig; on 64 bit: whatever you can afford.
A "playable" minimum would be dual-core 2-3GHz with 4 G RAM. Depending on your network connection (and missions) it will run 10-15 players pretty well, I guess.
Network connection will be 100mbit dedicated.