Define "doomed". Do you want to reuse passive speakers with Onkyo, or something else?
When I turn it on, it goes on "Protect" mode and when I took it to Sony service centre. After 2 weeks they told me that the main board has gone bad which has to be replaced and it will cost $220.
So I was thinking that instead of repairing that system, why shouldn't I buy a new receiver and use the Sony speakers with it.
The problem is that the Sony speakers have weird set of wires with a connector at the end so I don't know how to connect RCA jacks on them as there are 2 black and 2 grey wires coming from the speakers.
Get at ohm-meter, you can get a multi-meter for like $20. Measure the resistance across these two wires. If it goes between 4 and 8 OHms, you should be able to use just the speakers with your Onkyo (cut the connector).
You can also trace the wire inside the speakers, and see whether there is anything else but a speaker driver inside.