New, or Used?
Vintage or Recent?
With onboard DAC, and DSP Room/Speaker EQ processing, or a straight stereo preamp?
With or without onboard phono stage?
The great thing about Pre/Power combos, is that you can mix and match - choose the amp to best match your speakers, choose the pre to best match your inputs and processing needs.
AVR's and AV prepro's can make excellent pre's - especially if you want Room/Speaker EQ - cheapest way to achieve it for stereo! You get bonus channels that you can opt to ignore, many AVR's/AVPrepro's also allow you to use the additional channels for BiAmping, and the crossover processing is done in the onboard DSP.
In the world of old school stereo pre's I have always loved the Quad 34 /44 preamps with their "Tilt" control - in original form, not the most transparent (although no slouch by any means) - but they get a serious step up in some of the more recent refurbishings.