My advice is to do some more reading about how to setup a home theater system. Most displays do not have an amplifier capable of driving external speakers - you typically need an AV receiver or a "home theater-in-a-box" system that includes an amplifier and speakers as a package. Powered computer speakers can be better than nothing, but they are meant to be used in a computer desk set-up where you are sitting a few feet away, not to fill a larger room.
You're selling the Z-5500 WAY
too short lumping it in with the (typically) sub-HTiB quality of PC speakers
. I'm pretty convinced there is nothing in the (discounted) price range of the Z that even begins to approach its quality. It's criminally weak on features and inputs (1 optical, DD, DTS, and PLII are pretty much all its got), but there's a lot of speaker and sound quality for the price. I think original retail was like $600 on it, so it is not some anemic ultra value system. I have no idea why it is discounted so hard, probably because it's pretty old.