La Cumparsita is the right spelling, just as you have it. But I've never heard a strict tempo version of Libertango - I always associate it with Tango Nuevo and the Argentine style.

Have you heard of the GoTan Project? They are a group who perform what I've heard called Neo Tango. Do a web search or iTunes search and I think you'll be surprised at what you find. Another group who performs the same type of tango music is called Zum. The music uses all the "normal" instruments you're used to hearing such as accordians but it is very modern with a strong tango beat. Some of it can also be used for Hustle, if you like. Give it a try...I know I was pleasantly surprised when I first heard some of this music. It's wonderful!

http://www.thedancestoreonline.com/ballroom-dance-instruction/tango-music.htm