Used Audio Research Preamp Options

Before I pose my question, I do admit that I expect mixed responses since the question is somewhat subjective. That been said, I think I have pushed myself into an obsession to own an Audio Research preamp. I know there are better preamps out there for the money and I might ultimately overcome this obsession but I'd like to hear from folks who have owned different ARC preamp's over the years about their personal experiences. So here is my question: if you had $2500 to spend, which used ARC preamp would you buy? A line stage component would be fine, tube or SS. I'm also making an assumption which may not be completely valid and that is any of these preamps will be an upgrade from my NAD C165BEE. Any comments will be appreciated here too. My other components are McIntosh MC2200 (100K impedance) and a Vincent SP-331 ( 47K impedance,150w in 8 ohm/300w 4 ohm) amplifiers. Not sure if speakers matter- ML Aerius, Def. Tech. BP20 since I'm also looking for an upgrade route there too. Thanks.