Why don't you get a dual core server for about £80.00 with good spec's and then start it yourself? then you know you have full control and you get a lot more for your money.
You also control the games you want to sell and not to sell.
How your game panel looks and works.
TCAdmin is the best for Windows and gameCP for Linux.
I use TCAdmim and in my opinion it's the best for Windows.
You could always ask your dedicated server provider to help you set up the programs needed.
And if you want a free game panel theres: game create.
That works on both Linux and Windows.
If you need to know any more info just gimme a shout
Also top selling games I would say is: CSS, DODS, L4D2 and CS 1.6