After looking for some cases under your criteria, it was actually much more difficult than I thought.
There are alot of nice cases with side windows, but most of them have front door panels. Although this is a nice extremely inexpensive case you might be interested in:
<A HREF="http://www.newegg.com/app/ViewProduct.asp?description=11-156-019" target="_new">Raidmax</A> 268WSP - $42.99
I would also suggest going <A HREF="http://www.newegg.com/app/manufactory.asp?catalog=7&DEPA=1" target="_new">here</A> and just looking through the different manufacturers and start off by finding the ones that fit your needs visually. Then read the reviews for that particular case. That's alot of what I did when doing research for my case.
"<i>I'm seriously you guys</i>" - Cartman