Does good DAC improve sonics of low end transport

I'm embarrased to admit that I am unable to live without the features and convenience of my Sony ES 400 megachanger. I have a Jolida 202a tube amp with level I mods and an AMC tube-driven DAC9, Aura speakers and prolfex interconnects and Clearpath cables.

My real question is whether or not a good DAC will substantially improve the sonics of my crappy transport or will I always be compromising the sound no matter what I do because my front end is so inferior to the rest of my system. Is it worth upgrading other parts of my system with the transport, namely the Sony Changer, that I have now?

I would appreciate brutal honesty and please do not hold back on your opinions. Your advice will be greatly appreciated. Thank you.
The dac makes a large difference on the sound. Getting an aftermarket dac will help significantly. Dac's affect the sound of the digital source the most so it is a good investment. You can get inexpensive dacs from Channel Island, Scott Nixon and others or buy a good used dac for just a few hundred dollars and still have the megachanger convenience.
The right DAC will make a world of difference, however it would be a good idea to mod the transport to make it a good one or you will not get the real performance from the DAC. Most DVD players make excellent transports, but only when they have the digital output section modded. The impedance is usually screwed-up as well as slow risetime on the S/PDIF signal for stock players. The result is high jitter.

As for DAC's, you should lite on a Perpetual Tech P-3A or a MSB gold or Platinum. Both get a LOT better with mods. Once modded these DAC's rival and actually beat most SACD players when comparing redbook to SACD.
You will see a very noticable improvement, esp if you use a Monarchy DIP or a Genesis Digital Lens or other de-jitter device. I added a DIP and a Classe DAC to my CAL changer and it was a big improvement, even over a Class B CDP. I saw a Muse 3 w/4th order Bessel Filter selling for under $500 on the 'gon the other day. Former Class A and should really help your changer. I am not sure I would try to have the changer modded, but rather add the DIP and some good digital cables like Kimber D-60.
No question about it, a good DAC will improve the sound of a "crappy" transport. But its also true that a good CDP will sound better, too. What I'm trying to say is don't get carried away with a DAC to the exclusion of a good CDP. The "features & convenience of a good mega changer" may cost less in the long run because you are upgrading your transport and DAC without an added digital interconnect interconnect. Remeber the KISS principle (AKA, Keep It Simple, Stupid).
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Everyone is right, it will sound much better. The Musical Fidelity upsampling DAC is showing up for about $750. See discussion in Jan. Sterophile and previous test. When I had a cheaper transport I used to use a weighted disc which improved the sound. Try putting another CD on top of the one you are playing. If the drawer will work this way it will probably sound better. I have had good luck with the Mapleshade digital interconnect and it is not expensive.
I have one of the Sony ES Jukebox's and an outboard dac along with some other stuff in between. It sounds very good to me. I don't doubt that I could enhance the sound of my system with a real transport. But I fail to see the point if I am not going to listen to it. Bottom line is that I am too lazy to spin CD's every hour and I am sure as heck not going to flip LP's every 20 minutes, I don't care how much better it sounds.

Try a good DAC and a Monarchy DIP Classic and if you don't like the sound of your jukebox then you can get a single disk transport.
Yes, a good DAC will improve the performance of most stand alone multi-disc players. Having said that, i would echo the sentiments of what Audioengr stated pertaining to having the changer modified. I don't know anything about your budget though, so getting specific about DAC's might be out in left field. Either way, i would look for a DAC that has the inputs that you want and have it modified. There are many DAC's that are available on the used market that provide a solid platform to build upon. Sean
Jazzdude - you should consider getting the jukebox transport modded. Most Sony players make excellent transports once modded.
Audioengr - I would love to get the jukebox mod'd but in all my research I haven't found anyone who mods cd jukebox's.
Jazzdude: I bet i know someone that will "volunteer". And it's not me : ) Sean