This would be the best bang for the buck for a mid tower case. 49.99 - $20!
http://www.newegg.com/Product/Produc...82E16811139018
http://www.newegg.com/Product/Produc...82E16811139018
If you utilize more fan locations such as the bottom and sides it will cool every bit as good as the 300r.
The front is filtered through the sides I believe.
Well, for $30 after rebate, you could do worse than this case. I like them black and thick (8+ inches), without a lot of bling or attachments or flashing lights, and this fits the bill. Even with its front airflow deficiencies, it should give adequate airflow for low-powered/HTPC systems, and the thickness means clearance for tower coolers as well as about .71 inches of space behind the motherboard in which to stow cables.
If you are planning to run a higher-end build, the stock configuration kinda sucks. Bit-tech said temps dropped 6-9 degrees C just by taking the front cover off. The front fan can't really get much air through the sides and it really hurts the temperatures.
But you are right that if you mount some side fans it will probably be okayish. If you have decent fans at other mount points, bottom/top fans don't do much in my experience.
http://www.bit-tech.net/hardware/2012/02/10/the-big-cooling-investigation/10
Also, you could drill some holes or something into the front and toss a dryer sheet on it as a filter. That may help with airflow, but will also uglify the front.
From the comparison:Cooling sucks, they should have made a filtered front but nooo it's a freaking solid wall. Read the reviews
The filtered front vents are tucked away on the sides, which keeps the face nice and plain.
From the comparison: