Why a separate DAC?


Hello, I have a 3 yr old Yamaha CD player with Burr Brown DAC chip. What are the advantages of having a separate DAC? What would you recommend to compliment and upgrade this for under $1,500? Thank you.

Learning 
phill55
OCG HiFi (you tube channel) just compared 15 different DACs from $850- 23k+ 

I am currently using a Audio Alchemy DDP-1 (preamp/dac) + AS 5 (outboard power supply) It's a freakin bargain. No loner available new as AA introduced a new line, but I have seen the combo (the PS 5 is a must) used for $1700. Jump on that
Might want to check out the Mirror Audio Tubadour III. $1500. Tube output stage.
If you're looking for a separate DAC, I would echo those that recommend the MHDT Labs Orchid.  I'm listening to mine right now and it is my favorite out of some 10 or so that I have if you count all the CD players, and receivers/integrateds with DACS. 
I would like to thank everyone for their input, for someone who has gone from the solid state to tube experience with multiple amps and is now on the digital journey it looks like I will try to get a 30 day trial for the Mhdt Labs Orchid R2R NOS DAC! Will let everyone know how it works in my system.