I’m going to buck the trend here and recommend the P10. I have 2 high end systems in my home and turntables in both. My main system has Harbeth M40.1 speakers and a fully upgraded Linn LP12 with Radikal power supply, Keel subchassis, Ekos SE arm, Akiva MC cartridge, and Zesto Andros vacuum tube phono stage. My other system has Sterling LS 3/6 speakers, REL S5 sub, Rega P10 turntable, and Luxman EQ-500 vacuum tube phono stage.
Both of my speakers are similar to your Harbeth SL5 speakers. I recently upgraded my Rega RP10 to the Rega P10. Fremer’s review of the P10 is spot on and he loved it as much as I do. The P10 is much better than the RP10 or P8. The P10’s sound quality is in a league of turntables 2-3 times its cost. The P10 package deal with the Apheta 3 cartridge and RB3000 arm is a great deal and if you shop around, you can get around 20 percent off MSRP. The thing I really like about the Rega P10 package is that it’s engineered to work as a system (turntable, tonearm and cartridge) by the Rega engineers. The SQ of P10 is fantastic, providing stable imaging, with a wide and deep soundstage. Tonality, timber are lifelike. The P10 is dead quiet in operation and the Apheta 3 is a great sounding and tracking cartridge. I can’t stand any noise coming from my turntables and both my P10 and LP12 are silent operators. I highly recommend getting the P10 with the Apheta 3 cartridge.
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