I rent a Ubuntu VPS with 6 cores. This is not a dedicated server. Currently I get a speed of about 2.8Mkeys/s.
If you continuously use full CPU on a shared server, chances are your account will be removed at some point.
There's also
VanitySearch (Yet another address prefix finder), which is said to be faster, but I haven't tested it by myself yet.
TL;DR: you're going to want to use a GPU. Or, if you're looking for only one or a few specific address prefixes, you could use
split key so someone with a decent GPU can generate it for you. If you do this right, it is completely secure, and hiring a few days GPU-time from someone might be cheaper than running vanitygen on CPU for months.
Thank you for your comments.
I am currently using the VanitySearch program. I've tried four such programs and this is the most effective.
Would, in your opinion, using a dedicated CPU VPS be viable? Or is it more "any kind of CPU is a bad idea."
Are there any GPU based VPS that you can recommend? I have looked around and they seem highly expensive.
Would some kind of EC2 type thing work?