Well to be clear, I actually don't like the Sabre sound much anymore. I think it has its place with some types of music (notably very synthetic electronica and dance music), but overall I don't much like it. I'd rather have a TI or AK or Wolfson based chip if I'm going Delta-Sigma. My point was just that the worst things about the Sabre chip (the over-pronounced highs, the too analytical mids and the just okay bass) seem to be countered by the Cavalli house sound. So it makes the Sabre sound less bad. But starting with something that isn't as bad sounding to begin with is even better, you know?
Currently, the only way to get a cheap R2R DAC (that's not running the Philips chip, which I've heard isn't very good) is to buy vintage off eBay or buy on the classifieds here from someone who did that already. There are Thetas for under $400, Adcoms for under $200, etc. You just have to really be on top of it, like any good eBay hunt. Otherwise, the cheapest new one you can get currently is the Audio-GD DAC-19 for about $850. It's very good as a few of us in this thread can attest.
For non R2R DAC's under $500... you might check out this thread: http://www.head-fi.org/t/763905/finding-a-dac-for-the-cavalli-liquid-carbon-only-four-months-to-go