On the heels of launching faster DOCSIS 3.0 service and faster 50 Mbps speeds in parts of Rhode Island, Louisiana, Arizona and Northern Virginia, Cox says they're now boosting the speeds of their Preferred and Premier broadband tiers starting September 29. According to Cox, the company's Preferred tier will be increased to 15 Mbps downstream and 2 Mbps upstream. Their Premier tier will be bumped to 25 Mbps downstream and 3 Mbps upstream. Both tiers come with Powerboost, which will nudge speeds for the first part of a download or upload to 20/2.5 and 30/3.5, respectively.

Of course Cox is a carrier where all markets are not created equal, and the frequency of your upgrade schedule is entirely proportional to the quality of your local broadband competition. We know these speed hikes apply to Northern Virginia, but if you're in a less competitive market, your mileage may vary. We're trying to get some market by market clarification from Cox as we speak.

Update: "Northern Virginia just happens to be a DOCSIS 3.0 market but the Preferred and Premier speed boots are independent of that fact," Cox spokesperson Gwen Sparks tells us. "Speeds are actually set at the local market so timing of any speed increases varies," she says. "Some Cox markets increased speeds earlier this year and others are launching higher speeds later."