From experience, do not fall in love with just one PPC company.
You need to test your domains with different companies.
They all have their category advantages and dis-advantages.
But, if you are going to move around, you need to analyze where they do best.
Don't move for the sake of moving. And, don't move a lot.
You will also find that domains tend to pop when you move from one company to another.
Then, they settle down.
You should test some of the major ppc suppliers like DomainSponsor, Fab, Parked, NameDrive, etc.
If you don't have a lot of traffic, you will have very little clout with the ppc companies.
(I assume the mods will move this thread to the ppc section.)