You'll need a Xen VPS, as Xen usually use a baremetal setup, giving you a dedicated CPU core for just your vps.
I personally have used nfoservers.com's VPS and it worked pretty good for game servers. I'm using dedicated with another company, and the dedicated is MUCH better, but it was still playable on the Xen vps.
If you need multiple servers though, you could contact a GSP and see if they'll give you a discount for renting multiple servers.
10 slot game servers are doable on a VPS, but probably not much more than that. Your major problem will be getting access to dedicated processing power. Next on the list is if you have sufficient amounts of RAM. Disk I/O is not too much of a concern for a game server, along with disk space (srcds is only 5-7GB last time I checked)
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For the price of a decent VPS to cover the memory usage of the gameservers, I would have to recommend a GSP, atleast that way you(or anyone else on the box) wont suffer from srcd's fluctuations in mem usage.