At the moment this site transfers about 3GB a month, it is approximately 400mb in size. We have the capacity for 30GB of transfer a month and we can store up to 800mb of files.
The thing is that it's all pretty meaningless, all you have to do is try and find a good webhost and you'll be amazed at the choices, and if you look a little deeper you will see that there are lots of pitfalls too.
There's just so many bad hosts.
One.com do indeed seem to be really good, offering unlimited transfer and up to 4000 mb of storage space for the same price as I pay now, however I need to transfer admin rights for the domain to them if I want to swap from Petahosting.
Getting a deicated server is a non-starter too, they are at least $300 a month, the option I was thinking of was a VPS, which behaves like a dedicated server but again, the choice of these is bewildering.
The people we use, Petahosting in fairness have been generally great to deal with and thier uptime is approaching 99.9%, we do seem to lose about 3 hours a month, perhaps that's not such a bad thing, I dunno.
I guess that is about the best you could get when you are using shared hosting anyway. A future problem for us as we grow is going to be disk space. We will eventually need several thousand mb.
A site with 4000mb could be enough for us to be going along with, if we got any bigger than that then I guess that the next step would be a vps.