I ended up going with the VPS with 512MB RAM, single CPU core, 1TB bandwidth, and 30GB SSD.
This is because:
It was the cheapest option (even cheaper than purchasing a paid VPN service!);
It has a Gigabit connection, whereas the dedicated server does not;
VPN does not use much in the way of resources, besides Internet (it wouldn't have made sense to go for ...
The second VPS server has the most resources available to it, therefore it would be the better option. However none of the servers you listed will be able to run all three servers properly.
It should be noted that you might run into problems with only two CPU cores. Try to go for one CPU core per server (so at least three CPU cores).