Does the HR24 run cooler than a HR21-700

I was wondering if there is a big difference in the temperature of a HR24 compared to a HR21-700.  The combination of heat coming from my flat screen tv, surround sound receiver,PS3 and my HR21-700 it is like having a heater on in my living room. I have to have the a/c on even when it is cool out. I'm just looking for ways to cut down on some heat.