The systems I referred you to are complete replacements; sorry I misunderstood too.
I you want to buy replacements, you have two choices: find the exact same Sony speakers (with the proprietary connectors), or find 3 ohm speakers and splice them in (this is not a horrible option as long as you don't spend more than, say, $30.
You could get "standard" speakers and splice them in also. (Okay, so 3 options.) Problem is, most "standard" speakers are either 4 ohm or 8 ohm. if you get 8 ohm speakers they will sound very faint, and if you try to turn up the volume to compensate you'll almost certainly blow your receiver. 4 ohm speakers actually tend to be expensive, so they probably won't be an option.