This http://www.amazon.com/NETGEAR-Universal-Ethernet-Adapter-WNCE2001/dp/B003KPBRRW/ref=sr_1_1?ie=UTF8&qid=1387227901&sr=8-1&keywords=wifi+gaming+adapter is under gaming adapters at Amazon but it looks just like any other adapter?
I haven't ever experienced anything like this as I don't use my HT for TV etc, but isn't Dolby Volume or something supposed to cater for these things? Of course, even if does, it's probably as much of a PITA to have to keep turning DV on and off (you wouldn't normally want it on I am assuming) as it is to just adjust the MV. I do know there is no user control over Dialnorm so I believe your suspicion is right - there is no way to correct the current behaviour.
This site has statistics and details in incredible depth of just about every Bluray disc ever released.... except, well, guess.... ;)
Since the volume change occurs by simply exiting a program recorded in DD 5.1 to a music channel in PCM, there is no 4520 input change (e.g. it stays on DirecTV DVR), so Quick Select doesn't come into play.