I used the HTS 7.1 for many years before I upgraded to a Krell S1200. I know others who have used the HTS 7.1 as well. When used as a pure analog preamp, the HTS 7.1 is very nice, but I would probably put it somewhat on the soft side (due to its analog input section). That being said, it's still much better than the earlier Krell preamps such as KRC-2 / KRC-3 / KAV-250p. However, if you feed it a digital signal through COAX, the output of the HTS 7.1 is stunning! There's nothing wrong with the analog output section and the sound on this HTS 7.1 will still beat many current home theater processors! If you are streaming from spotify or CD using a bluray player (or other) as a transport, you'll get an excellent result through the digital input!! I would just make sure that the seller is guaranteeing the digital COAX input works fine, as I have seen these digital inputs fail after 15 years on the HTS 7.1. It would be too much money to get repaired based the $700 you are paying for this HTS.
If you want to get into LPs, you can still use the HTS as an analog preamp with a phono preamp for the turntable (HTS does not have built-in phono preamp). The sound may be even more soft and laid back than you are expecting (unless you want this result). You might be better off looking for a used Krell KAV-280p (newer than the 250p). The analog input and output sections on the 280p are awesome and it is definitely not soft / laid back like the HTS 7.1.