For your requirements, I’d also look at Fresh Roasted Hosting. Their VPS plans offer guaranteed resources, KVM virtualization, SSD storage, and a US-based Tier III datacenter, with the ability to customize resources as needed. Their current VPS lineup is more geared toward managed hosting, so I’d contact them to confirm whether they can provide an unmanaged setup with 3 IPv4s and CentOS within your $25/month budget.