Do I need a DAC?

Whether you'd get appreciably better sound quality from an external DAC depends a lot on the source material too.

Are you playing hi res files, CD rips or just 128kbps iTunes downloads?

Oscarrr, you don't need to be playing 24 bit files to be able to appreciate a better DAC. Most of my files are standard 16/44 and I find an external DAC necessary for the low cost sources that I use.

You could always just try a DAC and see if it does anything for you. Amazon sells several, to include Peachtree, Schiit, Musical Fidelity, etc. Just check the return policy for the vendor that you buy from. I believe that Wyred4Sound has a home trial program as well.

If you have the money to spend, I really don't think that getting a decent DAC can be a bad choice. It's more than likely that you will get at least some improvement. The question is one of how much.

As has been mentioned, you have a decent integrated and good speakers. All it would take for you to really get a bit more enjoyment out of the system would be to get a DAC and rip your CDs in a lossless format.

I'm not an audiophile and don't chase incremental increases in quality (although I'll take them if they pop up), but I never realized how enjoyable listening to music can be until I heard it through a decent system.