The DV-09 was great in its day. You really need to try both the blueray and the digital out to the denon against it. The 09 is probably 24/96 quality only. Due to the 09's age, I wouldn't spend much trying to upgrade its sound.
You really need to play all together first. If you are heading 2 channel, you may end up changing everything.
The sub is definitely undersized to handle the work for your system. Turn the volume on it down to reduce noise or just plug the port.
If you have $500 to spend or $5000, the best route is to listen to as much as possible first and see what you want most that you are missing. Then come back to the forum. However, since you are already set up for theater, why not keep it running but improve the amp and/or speakers. The denon should have preamp outputs?
You really need to play all together first. If you are heading 2 channel, you may end up changing everything.
The sub is definitely undersized to handle the work for your system. Turn the volume on it down to reduce noise or just plug the port.
If you have $500 to spend or $5000, the best route is to listen to as much as possible first and see what you want most that you are missing. Then come back to the forum. However, since you are already set up for theater, why not keep it running but improve the amp and/or speakers. The denon should have preamp outputs?