Actually the 500R supports internal WC as well just the config is different, although I'm using a CM 690II advanced, I'd totally recommend the 500R over the 690II as the dust filters are more accessible

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Added on April 19, 2012, 8:13 am
at this budget, forget about the enforcer & scout, I'd definitely choose either the 500R or the Trooper but take a look some others like the Fractal Design Define R3,  Haf-X and Raven R02-E as well

As bro Clem1982 recommended, Raven02-E will definitely be my pick. Having 3x180mm fan as intake. Superb cooling while premium looking.
I would grab it last time but the transparent window is on the right side which not suit me 
CM690II can fit dual 240mm fan at top and btm which is awesome for a mid tower but it will be very tight packed if you didnt hav good cable management.
The 500R does has a large 200mm side intake fan, but it is unfiltered, so its basically a dust hoover.
Anyway this isnt big deal, you can always grab or even DIY yourself a dust filter 
The main feature is HDD docking. Do you really need it ?
It doesnt hav front usb 3.0 port and quite poor cable management and only come with a 120mm fan which mean you need buy urself a few fans with some price.