I'll take a stab at this since I am currently going through the same process. First, I haven't heard the ELT LRS so I really can't comment on them specifically. I will pass on a few generalizations that I have found on PC Audio.
You have the same basic building blocks of a system:
1. Source- You will need a soundcard. From what I have read all on-board chips (with the exception of the Nvidia Soundstorm) use the AC97 codec, which will upsample anything that’s at 44.1kHz (MP3s and CDs) to 48kHz. The upsampling will cause distortion. Some factors in picking a card are: planned use of digital or analog outputs; if analog outpus what DACs the card has; reliability/stability; features; and of course cost. Some popular cards are the Chaintek AV-710, Audiotrak Prodigy, M-audio cards, and EMU cards.
2. Amplification- The amplification you decide to go with might be swayed by your choice of source and choice of speakers. Basic options are stereo receiver, digital receiver, integrated amp., and separates. The digital and multichannel circle here has a good discussion of the new digital receivers.
3. Speakers- In most cases the speakers will be used in a closer than normal sterep setting. I have seen some folks call it a nearfield setting. There are pro audio monitors that are made for this application. Of course you can also use normal bookshelf speakers. From what I have read in nearfiled settings generally you want speakers with smaller drivers and with the drivers spaced close together.
Some good sources of information:
AVS HTPC forum
http://www.avsforum.com/avs-vb/forumdisplay.php?s=e3b4daacb1d42920d17a9ecd3c1dda53&forumid=26Head-Fi Computers-as-Source Components forum
http://www4.head-fi.org/forums/forumdisplay.php?f=59 HTPC News Sound Cards Forum
http://htpcnews.com/forums/index.php?s=36cd9c0ac501f05ce798a7dd0f892600&showforum=10As I said I'm just working through this now, so if anyone has any corrections to my post feel free to point out any mistakes, including spelling.