There are such services, we may give a few tips if we can't sleep and are feeling masochistic (and of course there is a wealth of info on this thread if you judiciously use the search function), but you'll probably also need to do some experimenting.
I wish I was paid for the hour I spent typing my last post, all the time I've spent compiling reviews, and the money (not as much as Mad :P ) I've spent on gear. It's valuable knowledge, but I know that till I stop giving it out for free nobody would pay me. *shrug*
Far as processors that can bake-in surround audio into a 2 channel optical output, the only options for that are from PC. Overall, it's a long rabbit hole, your current gear can't do EVERYTHING so hopefully it does it well enough for you and the compressed audio material in videogames (especially consoles).
Edit: splitting your optical feed and building a separate audio chain for headphones is also an option, didn't know if you were willing to go that route. Knowing ALL your options is good tho, so yeah, you could also split your optical with that box, buy a surround processor like the DSS, send the analogue audio out from that to your vintage receiver, and have surround. I personally find SC very close to DH (have both currently but not compared head-to-head yet), and you may find connecting to the AVR's headphone jack to be a cleaner analogue signal than the DSS' analogue signal.
Ya make me want to experiment! Someday, *raises fist* I will get that Yamaha AVR back out from it's box!
Edited by Evshrug - 9/13/13 at 1:06am