I definitely have an HR24-500(I looked at the back). I definitely have a white DECA module box.
Today, I removed the white box, and plugged my router cable directly to the HR24, and hit the red reset button. Got on the internet just fine. My HR24 is 2 feet away from my router and modem, and I really didn't want/need extra cables and such in the area with everything I already have there(TV, stereo, DVD, xbox, router, modem, etc.).
The installer told me I needed the DECA box because the HR24 had problems connecting to the internet. The limited research I have done, has led me to the conclusion they only have problems when there are multiple receivers involved. Just saw that my bill is available online, and they charged me a $25 fee for "Internet Connection Kit." And apparently D* has no idea what the "Internet Connection Kit" actually means. I am now on my 2nd person on the phone, and they are still trying to figure it out. But I do not see a $3 fee anywhere on my statement. She put in a request to have the $25 fee reversed, but didn't say anything about the DECA box. She couldn't actually tell me how the charge got there, or what it was for though.
I looked at the other box in the coax, and it is a SWM module.