Realtek ALC883 Analog Vs. Radeon 4830 HDMI Vs. Envy24HT-S Optical/Analog

Hello...
I've been using a set of Logitech Z-640 computer surround speakers, for years, through the on-board Realtek ALC883 analog outs.
My first home theater receiver will be arriving in a couple of days and I don't have a clue what the best way to send sound to it is.
My first thought was to send optical from the mobo to the receiver, but I realized a couple days ago that my mobo doesn't have digital outs (I would have said it did, if you asked).
I have a radeon 4830 with hdmi out (I'm sending vga to a projector for custom resolutions, so the hdmi is unused).
I was planning to go that route, but then I read something about hdmi only sending 2 channel pcm and dts (I watch a lot of ac3/aac/etc... that I want to make sure stays in true surround).
A lot of that information seemed to be from the mid-2000s, though, so it may not be relevant.
I have an old Via Envy24HT-S pci card from a previous htpc that does have optical.
Maybe optical out of the envy24 is the best option, but if it has the same spdif limitations of the hdmi, then maybe straight analog is better.
Also, I'm not really sure whether the realtek or the envy24 would have better dacs, for the analog.
My understanding is the envy24's dacs were so-so, but I assume the realtek ones are equally so-so (although, maybe 5 years of so-so improvement is better).

So, given my mixture of audio sources, which would be the best means of getting audio to the receiver?
Again, this is my first jump into more "home theatery" sound so please excuse me if these are pointless questions.
Hehehe...
My logitechs have served me very well and made things very easy for a long time.
JJ

Edit...
A couple things that may be worth noting...
I run windows xp and use XBMC, generally, for watching movies and listening to music.
If XBMC isn't playing full speed (dxva doesn't seem to work - I may just need to configure some things), I use MPC-HC (dxva works just fine, there, but I had to configure some things).
I just noticed XBMC not keeping on a movie, for the first time, yesterday.
JJ

I didn't figure the receiver was important, but it is a Pioneer VSX-521-K.
If hdmi will, in fact, play multichannel ac3/aac/dts, then that's the way I will probably go.
I just wasn't sure by the information that I was reading.
JJ

Yikes...
HDMI cables are a lot more expensive than optical (of course, they do video, but not for my use).
30' optical is <$10 but 30' hdmi is >$25.
This is assuming the receiver will be under the center channel speaker (htpc is next to the couch).
I don't know if that would effect my choice, but it's good information to have.
JJ

Well, it looks like I might not be able to do multichannel audio, even it if was better.
Surprisingly, the vsx-521-k doesn't seem to support multichannel analog input (I saw multiple analog inputs, but the manual didn't say anything about combining them).
I figured this was a standard feature, since it was before digital, but maybe not.
JJ

I guess it must not really be that important.
It would have made things easy, though, since I'm already running analog from the computer to where the receiver will be.

Well, I didn't buy the receiver for those two options, so I guess it doesn't matter.
If optical will only do DTS and AC3, will HDMI do AAC?
I did notice that AC3Filter might convert AAC to AC3 in real-time, although I'd have to figure out how to make XBMC use AC3Filter instead of its default (FFDSHOW?).

I guess it's not that big of a deal to have a non-used secondary display.
It just seemed kind of pointless (I'd have to make sure no programs accidentally opened there).

It's not that far in a straight line, but 27'-28' is pretty accurate.
I have the computer sitting next to the couch on the open side of the room.
I could move it to the other side of the couch, but then it would be sandwiched between the wall and couch and next to a register (not good for heat).
I might be able to put the computer in the front, but then I'd have to deal with vga cable length to the projector.
I do have a lengthy vga cable, but it may not be that lengthy (I'll have to check, tomorrow).
If that works, then I wouldn't have to buy such a long cable for the audio part.
JJ

Well, this has been an interesting experience.
Normally, I would consider myself somewhere computer literate, but this has really kicked my balls.
Hehehe...
I couldn't get anything out of my hdmi, other than stereo.
I tried tutorials, programs, etc... and my dts/dd lights would never turn on.
Eventually, I found one post that said a guy was using windows xp without success and then installed windows 7 and it worked.
So, I gave that a whirl and it worked.
Personally, I don't care for windows 7 much (out of 7 computers in my house, all have xp).

So, my current setup...
Windows 7
XBMC (audio set to hdmi and 2 channel)
Realtek soundcard disabled in bios.
Ac3 and Dts do pass through (I get lights and proper center channel sound).
Aac (which I have a lot of) is still sending in stereo.
JJ

Hey now...
We all have preferences.
JJ