Meg, forget about the bandwidth. The costs of the next level are minimal, if any And going over 4GB for the site you describe is a TRIUMPH for your design! Don't dread, CELEBRATE. I don't know where you are, but I'm surprised that anyone is selling bandwidth as low as 4GB. Are you SURE that's not your storage space?

I'm a host. I won't give my URL, so use these number to shop around. Mine is $3.99 for 10 GB storage, unlimited bandwidth,24/7 phone support and I resell for one of the very biggest.

I would advise you doing a Google search for "unlimited bandwidth" and you'll get hundreds of them. But, no offense, I suspect you may not know how to tell a quality host from a rotten host! In maybe 15 minutes you should be able to sift through and find several hosts in your price range (they won't all be) Post them here and ask for recommendations, which is the politically correct way to do it.

Finally, if you have that concern, I suggest picking a host that will get you EVENTUALLY to unlimited bandwidth to an acceptable price. Unless you are REALLY tight for money, trust me on this, moving your website would be your biggest dread.

Good luck.