You might want to check if this person
still wants to buy some.
The Krix cost $600 new so I'd suggest start at $350~$400 and drop the price (if needed) if you get a nibble.
The RV 3900 is selling $1600 (official manufacturer refurbished) but also available around $600 used on ebay US. Really depends if you can find a buyer. If you're selling via ebay maybe take a punt at around $1000 and see if anyone will bid for it from there?
The S3 available new around $1100. I'd have thought sub woofers would hold value reasonably well. Maybe around $600.