Ever since Howard Stern left in 2005, CBS Radio’s WXRK FM has been in a tailspin. It briefly flirted with an all-music format in the form of Free FM, and then went back to its “active rock” roots when it hired Opie and Anthony (who also have a show on XM Satellite Radio) to host its mornings. Now CBS is changing the station yet again, as it has slipped to 21st place in the New York metropolitan area. It will be re-branded as Now FM (92.3) and will play Top 40 music, to compete with the region’s No. 2 station, Z100. Z100 has been the top choice for pop music in the city for several decades now. Opie and Anthony will no longer broadcast in the city, so fans will have to sign up for XM to hear them. “Extremely bummed,” Twittered Opie (Gregg Hughes). “This is not good for our show, period!” We’re sure XM loved reading that.