Let the hive mind of Engadget get that for you.
"I've found myself using my PC for a lot of conversations lately, and I'm also considering recording a podcast to share with anyone who will listen. There are tons of USB headset / microphones out there, and I'm hoping someone has some solid recommendations based on experience. I'll consider both headsets and standalone mics, by the way, but I'd like to keep the bill under $100 if possible. Help!"
Actually it doesn't - the HR20 has 1 ATSC tuner and 1 satellite tuner
The HR21 has DUAL satellite tuners, and with the addition of the AM21, TWO ADDITIONAL ATSC tuners - for a total of QUAD TUNING CAPABILITY
I wonder if the combo will allow for 4 recordings at once?