Rega RP8 cartridge?

At this point, Lyta cartridges are clear winners. Any other sub $2000 contenders [MC].

The Rega apheta is an excellent sounding cartridge, Big dynamics and resolution. Mounts well with the rp8. One of the best with rock and progressive music

The Delos is a very significant upgrade from the Denon, but you will have to raise the arm significantly to accommodate the extra height. As I recall, you may need 3-4 Rega shims. I personally had no problem with that, but some people don't like to change the Rega arm height for some reason. I'm not 100% sure, but I think the Goldring Eroica MC may well work in the Rega without shims or less anyway. It's a very nice cartridge for under $1K, IMO.

I have a Zu 103 on my RP8 with a Groovetracer counterweight. I think that they sound fantastic together. I'm fairly certain that the Zu guys take that combo to most of the shows. That combo would come in well below your budget. It's a great match as long as you have a solid phono preamp.

The Lyra Delos is certainly an outstanding cartridge in that price range, although I am using it on my LP12 and not on my RP8. For those who are using the Delos on a Rega turntable, how many spacers are you using? I suppose 2x2mm is the obvious choice although I have read that 3.5mm is preferable. The Delos (and Kleos) more than many other cartridges is particularly susceptible to correct VTA due to its design.

If you can find one, the Benz Glider is also a great match with the RP8 (with 4mm of spacers), although it is no longer made so may be difficult to find.

I sold the Apheta that came with my RP8 - I just didn't like the sound.