I got a pair of aluminum die cast car speakers for a car once that sounded great & were reasonably priced.
I think they had a 4" to 6" speaker & a tweeter in each cabinet.
About 25 watts each. I would think that 2 or 4 of those might make a great computer speaker outfit?
Maybe a 120volt quad home sterio (4 channel input) as an amp. (front & rear speakers like a car?)
If you have an amp in mind and have the time to shop around at an auto sterio shop, you might find something.
Edit addition:
The speaker cabinets were die cast aluminum, about 10" x8" x8"
They cranked with clearity & bass so I thought I would suggest it
in hopes that some one else has tried it with results to report.
I'm doing about the same thing now with a 75 watt Fisher power amps (am/fm digital reciever)
using boom box speaker, small home speakers & the speakers out of a big screen tv (two 6" w/tweeters)
I kept trying different speakers I had laying around untill it sounded great for music & games.
Big speakers wern't great for games. Little ones were great for music.
But I didn't try my car speaker selection, darn it.