If your Onkyo has two sets of speaker output terminals (a total of 8 speaker terminals) you can connect your DAC to it and then connect it to your speakers. Don't hook up two sets of speakers to the same speaker out terminals.
If you want separate amplification for your music only, if your DAC doesn't have a volume control you will need a preamp to control volume, etc., and then a power amp to drive your speakers (or an integrated to do both).
For $1,000 you can get a pretty good integrated amp (preamp and power amp in one box), tube or solid state. I think the best bang for the buck would be an integrated.
If your DAC does have a volume control some people like to connect their DAC directly to a power amp, skipping the preamp. Other people find that their system sounds better with a preamp (or integrated) in the system.
If you want separate amplification for your music only, if your DAC doesn't have a volume control you will need a preamp to control volume, etc., and then a power amp to drive your speakers (or an integrated to do both).
For $1,000 you can get a pretty good integrated amp (preamp and power amp in one box), tube or solid state. I think the best bang for the buck would be an integrated.
If your DAC does have a volume control some people like to connect their DAC directly to a power amp, skipping the preamp. Other people find that their system sounds better with a preamp (or integrated) in the system.