How hot CAN the universe get?

Ever since learning about absolute zero (the temperature at which no heat remains in a substance), I always was curious as to whether there was an analogue on the toasty end of the spectrum. Is there a limit to how hot a temperature can exist? I never had a physics teacher who could answer that question, but the internet today “has done it”:http://www.straightdope.com/classics/a3_347.html:

“The highest possible temperature, called the Planck temperature, is equal to 10^32 degrees Kelvin. For comparison, the center of the sun bubbles along at 15 million degrees K (15 x 10^6); silicon can be created by fusion at 1 billion K (10^9).”

Thanks to “The Straight Dope”:http://www.straightdope.com/classics/a3_347.html for finally answering this question that has bothered me for years!