A Team Fortress 2 server uses about 500MB of ram for a 24 person server, with SourceMod and a few basic plugins running. The storage space you have is more than sufficient for 3 servers, as long as you aren't loading a ton of giant, uncompressed maps. The 8000GB of bandwidth will be fine for 3 servers. (I've run 14 servers on a 10000GB line, with a fast download server and never gotten close to 8000GB in a month). Compress your maps. You'll keep your bandwidth usage down and your players happy - downloading a 10 MB map is much faster than a 70 MB map.
The problem you may have is that you only have 2 cores. If you are running vanilla servers, you'll be fine. If you are running heavily modified game modes, you may experience issues.
It's also worth noting that MvM is very processor intensive. If you are running a MvM server, you will not be able to run 3 servers with only two cores.
I'd recommend the package you are considering, provided that:
- You are not running an MvM server
- You are not running a mod like dodgeball and a lot of projectiles. A single or double projectile game should be fine
- You know how to compress that maps to save bandwidth