When numbers start getting up into that territory, I tend to look at the discount dedicated servers.
WholeSaleInternet for example, currently has a Quad-Core Xeon E3 1230 for sale at $49/month with 5 IP Addresses. 1GBPS connection with 10TB bandwidth with 8GB of RAM / 250GB of Hard Drive.
If that 2TB Hard Drive is really needed, you can compromise on the CPU and go for a consumer-grade AMD Fx-4100 (Quad-Core AMD) from Datashack for $55 / month, with 5 IP Addresses, 8GB RAM / 2TB of Hard Drive space, 10TB of Bandwidth on 1Gbps
Most web applications seem to be Disk heavy or RAM Heavy... I rarely see CPU-heavy applications. So the AMD Fx-4100 can be good enough (its far far better than an Atom, although it isn't as good as a modern E3 Xeon).
I've never had the need for it, but since Dedicated Servers often come with 5 or 13 IP Addresses, and they can be as cheap as ~$60/month realistically... I think its better to just install Proxmox on a single dedicated box and spin up your own private VMs if you are honestly going to need multiple VMs.
Exactly, for that situation, I ended up going with an entirely overpowered dedicated server with an E5 and 32GB of RAM. I shopped around, but was very conscience of network quality, quality of support I'd get, and was still able to get away with paying about $250/mo, which is very reasonable compared to any kind of cloud offering.
I run a service that could get away with only 8GB of RAM, but definitely needs at least 2TB of space, plus plenty of room to grow.