Unfortunately the site you are asking for is the HOLY GRAIL of music sites. I've given up looking for a site where one can buy individual songs for less then 89 cents per song.
I buy all my music at Amazon.com's MP3 store: 89 to 99 cents per song and slightly less if you buy the entire album (depending on the size of that album and that most albums cost about $9.99). No DRM and no limits to how many computers and MP3 devices one can place the music on. Plus it's at a higher bit rate (higher quality music file) then that of the higher priced iTunes.
I guess one of the music subscription sites where you pay about $14 or 15 a month for unlimited songs might be the way to go but you lose access to the songs once you let your account expire.
Hopefully someone here can name drop some of those services. I can't remember their names right now and I never used them either.