..loved the Rega Isis when I got one of the first off the line (not got one anymore - that's another story in itself, I still respect Rega in what they do as well as true professionalism of Paul Darwin, a complete gent and thoroughly nice guy).
I had heard a Versalex getting on to be nearly a decade ago, can't remember what it sounds like now. Got a dem booked for a listen of a P8.
It's very difficult. From listening to what you want from Vinyl, it's exactly the same as my goal and I still think you'd be very happy with a good LP12.
There is a big difference between how impressive something can be initially, or in a dealer dem, and what it's like to live with long term. When I first got the RP10 I was seriously impressed with it. In technical respects it was better than the LP12 in every way. It was cleaner, clearer, more detailed, had great speed stability, crazy low surface noise and just seemed far superior. There were things I wasn't sure about, it seemed lean and cold, but I assumed I'd be able to find a cartridge or adjust the set up and get it where I wanted. I fought with it for two years but never did.
I've heard the P10 in shops, sometimes sounding terrible but other times great but the times it sounds good it's playing a well recorded jazz record or similar. When you dem the P8 don't let them do that. Take the records you want to play, and not the great sounding recordings. Take the music you like that isn't well recorded.
So I decided to try another LP12. I hoped that if I could get the spec right it'd be happy with it, I expected to need to make a few changes but I was very blessed and got it fundamentally right straight out of the box. Well I built it myself but you know what I mean ;0) The scary thing about the LP12 is also its greatest strength. You can tailor it to exactly the way you want it to sound. You just need to know what you want, and I think you do, and know someone who knows how to build an LP12 to sound that way. With modern parts they are much more stable and consistent than they were years ago and sound great. There is literally nothing about the RP10 I miss. My understanding is that the P8 and older RP10 are very similar in performance by the way with the P8 maybe being slightly better.
I've never heard an Isis but I have a Saturn-R and I love it. What is weird is that it does not have the clinical, emotionless sound of the RP10. The Saturn-R makes you love the music, an LP12 makes you love the music, the RP10 made you impressed with the music but un-moved. I genuinely got more involvement from a P1!
So tread carefully. Don't bet the house on a dealer dem. Listen to an LP12 beside the P8 if you can but I'd be inclined to buy used kit so that you can live with it for a while and sell again if you don't like it. And don't let the bartwards play you jazz! That should be my tag line ;0)