I've toned down our initial estimate of 16 GB as I don't plan to launch with 150 players. However if 4 GB really isn't powerful enough I'll run it on a 8 GB with 50 players. That should be more than enough.
I'm telling your right now your going to get ddosed to hell so prepare for this. Also a bit off topic i know bitvegas had a copyright so you might want to not name it the same thing because you could get in legal trouble. Check if the copyright expired/
We're called BTCVegas, not BitVegas, however I will remove references to BitVegas in the OP to prevent legal trouble.
We will see what we can do about DDoSes.
Like I said in an earlier post, I can develop you some custom DDOS-prevention software. Let me know if you're interested and I can outline how it might potentially work. I think it would be really easy to integrate with your website and effective at preventing attacks.