Business/Business Casual Case for Inspiron 1720

I recently bought my first laptop, an Inspirion 1720, as I'm going to start taking some online classes in a couple months to work toward a career change. My current workplace is business casual but I may end up in a more suit-and-tie type environment in a year or two. I need a laptop case that will fit in in either environment but I'd prefer something a little less boring than the standard issue type business cases. I need a case that has excellent protection for the laptop plus room for a cooling pad, extra battery, full size mouse, charger, one textbook, a notebook, and a couple small pockets for odds and ends. However, I don't want something huge and oversized. I'm looking for just enough space to fit those things with minimal bulk. There are a few I've seen that I like but I don't know if they'll occomodate my needs.

Examples:
Mobile Edge 17" Premium Briefcase
Targus CityGear Los Angeles
Microsoft Edge
Case Logic Slimline

The Mobile Edge is my favorite on the list. I just don't know if it will hold everything I want it to. It seems to offer good protection, though.
The other three are just examples of what I like from an appearance standpoint. If anyone can offer opinions on how suitible these bags would be for what I need or suggest others it would be greatly appreciated.
Budget is <$100, prefer <$60. Waterproof/resistant would be a huge plus.
Though I'm not particularly fond of the look of it, the Tom Bihn Empire Builder with a Brain Cell would be perfect for what I need. Unfortunately I just can't justify spending that much on a bag at this point.

Thoughts?