Budget DAC for Oppo VS. Orig. Rega Planet

I have an Oppo 970 and someone had suggested getting a separate DAC for my Oppo to improve it. What would you suggest in a separate budget DAC and digital cable? Would the separate DAC/Oppo combo be better sounding than if I just sold the Oppo and got an orig. Rega Planet? Overall, I've been pretty happy with the Oppo, although it is a little lightweight sounding. Thanks for your replies,
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That url is http://www.pacificvalve.us/
For some "budget" means $200 - $300 but I believe one of the best "budget" DACs is the Channel Islands Audio VDA 2. I love this DAC, for $599 you'd be hard pressed to find a better sounding or better built DAC.

Assemblage 1.0 or 2.0. $150-250.
For $180 shipped the Valab NOS dac is a strong contender. I own some much more expensive cdp, but this is a musical budget dac that I could live with. There is a review here on audiogon and lots of discussion on Head-Fi as well.
I would support the move to a DAC rather than an upgraded CD player. Much more flexibity for the future should you want to upgrade your transport or move to a server/pc based system. Personally I prefer the sound of NOS DACs and there are many good budget ones often named around here (MHDT Paradisea or Havana, Keces, Valab, etc.) You could also look at upsampling models such as the Cambridge DACMagic or one there seems to be a lot of noise about on Head-fi by Audio-gd or as Oddiofyl suggests, the CI Audio VDA 2.
I would have to also recommend going with a Channel Islands Audio VDA-2. That is what I ended up using with my Oppo DV-970 after trying several different DACs from MSB, DIYEDEN, California Audio Labs and Benchmark. The Oppo seems to need a high quality external DAC in order to hear an appreciable positive difference. Another thought is looking at one of the tube DACs by Pacific Valve & Electric Company at www.pacificvalve.us. Then you can tube roll to your liking. Or check out one of their less expensive solid state DACs that they rate well.
I went through the same process as you. I had a 970 and added a Bencmark DAC1 to it vs. modding the 970 or buying the Planet. The sound is beyond belief in presentation, musicality and involvement. My next step was to purchase a used original Planet to use as a transport, until hard times came and I was forced to sell the DAC. Incidentally, the 970 has a very good transport, one of its strengths.

To get the best sound from the 970 set the digital out to RAW (use PCM for movies), the speaker output to L&R (not stereo) and the upsampling to 96 khz (44 is to flat and forward and 192 has too much space with a light bass)and your good to go.