Dedicated is the way to go in your situation. Even if you could find a plan and a host willing to handle you in a shared environment, you'd still probably face the same situation again in a few months. Going ahead and getting a dedicated server is the right way to go about it.
I'd suggest contacting each respective company you're interested in about advertising in order to lower costs. I'm sure that there are companies out there who would at least cut costs somewhat. Even just a banner can be fit into the page where it's not too obtrusive. WHT is a great example, even though you do see the ad, it does not get in the way and for someone like myself I don't really notice it anymore.
You said in a later post that you were only looking for 3G of space not 30G. So you are looking for total resources of 3G/40G? That would fit into a reseller plan, but your CPU load is the problem, if I understand you correctly?
You might not need to go to a dedicated server, check out some of the VPS plans around that give you your own chunk of RAM and the CPU.
i am not to happy with it .. but it was a trade off .
or go with an expensive server
or go for a cheap one and do everything under redhat yerself .
lucky enuff i got a linux wizard helping me out free of charge but i wouldn't recommend it to users who have zero linux/sql knowledge .
i was hoping to port over the whole show b4 the E3 in LA but that is gonna be a no go .