Audio Research DACs

Audio Research usually doesn't mention much about their past line of products on their web page, so only current products are mentioned. I know ARC has the DAC3, DAC1, DAC5, with the DAC3 being the current version. Does anyone know the history of these DACs as far as sound, quality, etc. I am assuming DAC3 is the best since it's current, and as with DAC technology, USUALLY more recent is better...What would be the comparison between DAC3/DAC1/DAC5?
Have not heard the DAC1. The DAC2 has a solid state output stage, the DAC3 a tube output stage with predictable differences. The DAC2 has more powerful, defined base and the DAC3 a smoother, more harmonically rich midrange. I prefered the DAC2 for rock, the DAC3 on almost all other music, and bought the DAC3.
How does the DAC5 differ from the DAC3?
Correction: Does anyone know the difference in quality between the DAC5 and the DAC2?