Get a new CD player or external DAC?

Check out the TADAC by Tube Audio Designs.
Qualifier: I have no association with them/TAD other than being a satisfied user of their product.
Good Listening!

Thanks for all response, your recommendation will be further studied for consideration. I forgot to mention my music taste is towards musical, warm rather detail and analytical.

@Chewy - CA 840C is in my first priority list as it serves as CD player + external DAC (with its digital input).

@Mimberman - Though i have ripped all my CDs into lossless files, i still listen to my CDs occassionally, in term of ratio between SB3 and CA 540C, it's approximately 60 : 40.

@Dokosan - Benchmark DAC1 USB is my first choice of external DAC, is it more musical, warm produced by your system after adding Benchmark DAC1 USB? What is the different between Benchmark DAC1 USB and Benchmark DAC1 Pre? The obvious i can see, the latter provides more digital inputs.

@Tobias - Noted, digital cable (coaxial or toslink) is crucial. What about analog cable (analog output from external DAC to amplifier)? Krell KAV-400xi provides balanced analog input (XLR/AES).

Auronthas - You're correct that the DAC Pre adds analog inputs; that's the only difference. I am running DAC 1 in balanced mode into the 400xi. My understanding is that balanced is the preferred choice but I can't give you the technical explanation other than the gain is slighly higher.

I would not say that introduction of the DAC 1 warmed up the system. This DAC is noted for being very detailed and accurate which is what I was seeking. If you are looking for a warmer sound you may want to consider some of the tube dacs (wavelength brick is in the same price range). There seem to be a lot of new USB dacs coming to the market such as Musical Fidelity and Cambridge.

If you make the move to a DAC, you may find yourself never handling a CD again other than to put in your car (unless you have a car with an ipod jack). It is extremely convenient.

If you are looking for a warm sound from a DAC then you could go with an MHDT Havana. I really liked it when I had it in my system, although if you're switching sources frequently it's not the most convenient since it has no input select switch. I preferred the Havana to the wavelength brick in my system. I know people also like the dacs from Ultra Fi and Red Wine Audio. The Benchmark is a much more analytical sound. I had one and it didn't mate that well with my old system. The Bel Canto which I have now isn't tube warm, but I find more organic than the benchmark in my system. I'm running balanced as well.

Auronthas, the Benchmark DAC-1 is an extraordinary product. I have
compared its sound carefully with that of two other DACs at equal or higher
prices. I found it brought out details in the recording like nothing I had ever
heard. Get a listen if you can. If you can't, and if you prefer warm over
analytical, then I would bet you took to the Apogee Mini-DAC more than the
Benchmark. Both have XLR outputs.

The situation with digital cables is rather special. The point here is that any
digital cable will do its best in most setups only if it is 1.5m long. A cheaper
cable of that length will beat a better but shorter one for coherence and
clarity. Analog cables don't have this length requirement. The shorter you can
make them, the better they sound.

With any cable, buy the best you can which still keeps cost in perspective.
The idea is not to pay for cables with money you would be better off using for
a major component upgrade.