I had some Calipers many years ago and got excellent results using passive biamping with 2 amps.
Your best option is to passively biamp the speakers with the 2 DR9's.
Use 1 amp for each speaker, using the left channel for bass and right channel for mid/top.
You will need 2 sets of interconnects from your preamp to the power amps or buy a "Y" connector if your preamp does not have 2 outputs.
This configuration will be a substantial improvement as it delivers more current to each driver than 1 amp or bridging the amps.
Your best option is to passively biamp the speakers with the 2 DR9's.
Use 1 amp for each speaker, using the left channel for bass and right channel for mid/top.
You will need 2 sets of interconnects from your preamp to the power amps or buy a "Y" connector if your preamp does not have 2 outputs.
This configuration will be a substantial improvement as it delivers more current to each driver than 1 amp or bridging the amps.