I've gone to hdd based. but i use to use sony ES 400 Disc dvd changers that i had daisy chained (3 Of them), and then had an extron switcher hooked up to a pc and those plugged into the dvd changers and i used cinemars dvd lobby to control all the dvd's. it would chose disc location, player etc.. they also have\had plugins to work with jriver for dvd and music. but it's been years since i've been over there.. so not sure if they still support it or support blueray\HDdvd.. but may be worth a look if thats the way you want to go...
Reason i switched over was the money i had invested in the ES changers and the extron switcher, cables, etc... It behooved me to go hard drive based (Price of HDD's went down considerably), and after being down that road I'm glad i switched. and would never go back.. Personally i could\can do a lot more customizing PC based. and the files are there Instantly.
Anywho.. check it out... lots to read about over there too about HTPC stuff. (Forums)
Hope this Helps.