I have not heard the CA 840 nor the Teac 2000 but do own the Yamaha A-S1000, and love it. Dead on neutral sound signature with Klipsch RB-75's and plenty of bass drive for it's "90w@8ohms/ch" power rating. I do own and occasionally use a CA 640A v2 and it too is pretty neutral and has decent low end capabilities.
Bill
Bill