RackSpace is probably the most reliable and the best for management wise. However it is also the most expensive. Dinix is quite good, I have not seen any complaints on these forums. They use pure internap bandwidth which just is absolutely amazing. However out of all those, the most cost-effective one would have to be servermatrix or the planet. I've been with them for a number of months and everything has been going well. Of course there are a few problems here and there, but you'll be ordering managed services which helps a lot..
From what I have been hearing personally Rackspace sounds like a solid choice eventhough I have not had very much experience with them. Also I have been able to speak to Server Matrix quite a bit and they should be able to come up with some sort of solution to fulfill your needs as well. There is a wide variety of companies to choose from depending on your specific needs and the level of management required.
If you are looking for a company that will just checkup on your box from time to time opposed to a company who will maintain and keep your box up to date, you will notice that the variety of choices you thought you had just slimmed.