Will a new Dac improve the sound?

I have the best DAC I have owned, the Audio Research Reference 9 CDse. I had the $22K Berkley Alpha Reference 3 DAC in my system and the sound was really really really close… a tiny itsy bit different… the ARC was a touch warmer and the Berkeley a tiny more detailed (took hours of critical listening to be sure). This is an all ARC Reference system that is extremely detailed, and natural sounding to start with. See, my user ID.

On the other hand I had a very good high end Sim Moon DAC and it was thin and cool in comparison (this is a good DAC… we are talking about high performance stuff)… I said in comparison.

A high quality tubed component is a thing of beauty. But it is one component in the signal path. A very good one to have tubed… but so is a Preamp, and amp. To have a really natural and complementary system, all tubed gear is a good way to go. Not the only way. 

I have a Cary 303, which I believe is older and more expensive than the cdp1. I use it as a transport for a bricasti m3. The m3 is a giant reduction in distortion from the 303 dac. Smoother and more detailed, a huge improvement. as a transport the 303 is better than my iMac through the Ethernet input. 

In decades past I used transports with outboard DACs. Being retired for 5+ years living on SS, I streamlined my front end , making due using my Oppo 105 (with aftermarket power supply). The following worked out for me because I have an Audio Alchemy DDP-1 + PS 5, a dac/pre. So, then I used an old Pioneer PD65 with level 3 Musical Concept mod as a transport (but it only had toslink out) for redbook, and used that until it died. I replaced it with a Marantz HD CD-1 player, used as a transport but with coax out, but like the PD65, the laser mechanism died, parts are no longer available, BUT, I could buy a laser assembly for $150 + shipping from Asia. However, I came across a fantastic review of the Audiolab CDT 6000, and found a slightly used one on AG at a price I could afford. The level of improved musical enjoyment jumped quantum levels, still surprising me months after the purchase. From my experience, unless you have an exotic ($$$$$) player, it likely has an average laser mechanism and circuit

hth

Yes it will. I made tests with different CD players. A separate DAC, even a modest one,  will give you a notable difference. If the DAC in your CD player is not really good and you choose a good DAC, the improvement will be very essential.