Yeah the one you pick. Seriously there are dozens of bags out there that would fit the bill. Go to a good photography shop and look around and see what you like or check out this site: Reviews - Cambags.com Camera Bag Resource.
What you like and what I like can be two totally different things.
Did you got to cambags.com? If so you can go to the "bag size" tab and select the type of bag you are interested in then select to look at bags designed for 1 body and X# of lenses etc. I have Tamrac, Lowpro, Pelican Thinktank and Billingham bags all for different purposes.
Who ever told you that Photography was going to be a cheap activity LIED!
All of my suggestions are going to be in that same kind of price range. In your price range you might want to look at manufacturer bags such as Canon. Canon has a shoulder bag and a backpack. Don't know about other camera manufacturers. You might look at these.
There is a Kata bag in the for sale section on this website- I have one and love it. Maybe a bit more on your budget, but it fits what you want exactly.