DAC in a simple system?

When compared to most here, I have a very modest system. For digital, I am using the Marantz 5003. I was looking at the Musical FIdelity V-DAC. The brand seems to get a lot of negative comments here. I have a couple of their x-10 v3 buffers which I really like.

The big question here is will the $300 DAC really make a difference? From looking at specs, it would seem that the internal Marantz DAC has pretty much the same specs; however, everything I read about external DAC's makes me want to give it a shot.

Thanks for the read and any possible hints,

jd