I see 16 of these on my VPS (YMMV depending on how long ago your VPS was created:)
processor : 15
vendor_id : AuthenticAMD
cpu family : 21
model : 2
model name : AMD Opteron(tm) Processor 4386
stepping : 0
microcode : 0x6000836
cpu MHz : 3100.038
cache size : 2048 KB
You may say that these are not the latest models but do they achieve the purpose of keeping thousands of customers satisfied? Most of the time, yes otherwise we wouldn't be in business. It all depends on what your needs are. Let's talk about those first.
VPS are not necessarily meant to be poweful. The main difference with the shared server is that the hardware resources (RAM, CPU, disk) are a lot more isolated between customers. And there is more of those available in a VPS compared to a shared server.
What kind of applications are you running? What kind of loads do you have? It's impossible to give any meaningful suggestion without specific needs. Real life applications and precise measurements are the only metric that really counts, and every reputable CPU comparison/benchmark will say that. Share more details please and we can give you useful suggestions.