I see the complete series of The Wire for $45 on ebay:
THE Wire THE Complete Series DVD 2008 23 Disc SET 883929023196 | eBay
Maybe get the first 2 or 3 episodes off itunes (@ $1.99 each) and see if you like the series. Or download it somewhere.
A lot of people don't like Season 2, but otherwise it's considered really strong the other 4 (I personally find Season 2 amazing though). It's a really ugly portrayal of the Baltimore PD from a Baltimore PD homicide detective, but they're still shown as the good guys for the most part.