Definitely do your front end first.
You might also want to look into PC Audio if that holds any allure to you (having your entire music collection at your fingertips. If done right that method can also sound better than "very good CD players". Yes, you certainly could get a nice DAC and use your current transport, or a better one. A great DAC will make a significant difference to my ears. I don't know how discriminating you are. My wife couldn't care less about this stuff and claims to hear little difference. It's in the ears of the beholder, as it were. It would not be difficult to improve upon an older Onkyo DVD player IMO. To clarify what may be confusing you: Your CD/DVD player already contains a DAC inside. If you used it as a transport you would be bypassing the use of that internal DAC by sending the digital output signal to an external DAC (assuming it has a digital output) via a cable. By all means, it can make a big difference. I'd probably go for a better transport too, especially if yours is old. If you don't have much experience in these realms, I'd suggest you go to a dealer, or to an audio show where you can hear a few examples and see if the differences made in an investment in your front end actually matter to you (or that you can hear them at all). If you have a friend, or a local audiophile club, or anyone who might be patient enough to demonstrate to you what potential may be there for you that would be a big step in the right direction and may save you money, and or open up new worlds.
Although I have also read that a decent cdp used as a transport, and a dac such as the bel canto dac 2, sound nearly as good as some of the very good cd players out there.
You might also want to look into PC Audio if that holds any allure to you (having your entire music collection at your fingertips. If done right that method can also sound better than "very good CD players". Yes, you certainly could get a nice DAC and use your current transport, or a better one. A great DAC will make a significant difference to my ears. I don't know how discriminating you are. My wife couldn't care less about this stuff and claims to hear little difference. It's in the ears of the beholder, as it were. It would not be difficult to improve upon an older Onkyo DVD player IMO. To clarify what may be confusing you: Your CD/DVD player already contains a DAC inside. If you used it as a transport you would be bypassing the use of that internal DAC by sending the digital output signal to an external DAC (assuming it has a digital output) via a cable. By all means, it can make a big difference. I'd probably go for a better transport too, especially if yours is old. If you don't have much experience in these realms, I'd suggest you go to a dealer, or to an audio show where you can hear a few examples and see if the differences made in an investment in your front end actually matter to you (or that you can hear them at all). If you have a friend, or a local audiophile club, or anyone who might be patient enough to demonstrate to you what potential may be there for you that would be a big step in the right direction and may save you money, and or open up new worlds.