Pro-ject vs Rega

We need some hint on your values in sound quality and the rest of your system, maybe the kind of music you listen to.

Theres a place under your UserID to put some photos of your system and ID your components. This is really helpful for us.

I love warm, smooth sound. I’m listening jazz and blues. 
I have accuphase e 280, speakers kef r7, I will buy external phono stage depending of which turntable I’ll choose 

Go with the Rega. I have had a P9/RB1000 for over 10 years and never an issue. You will get synergy with any Rega cartridge and all Rega tables respond well to upgrades. The P3 has an option for an external power supply, replace the felt mat and even consider upgrading the feet. I added Spiral Groove feet to my P9 that added a refinement/clarity without taking away the Prat Rega is known for.

One benefit to the Project X1 is that the arm has adjustable VTA, whereas with the Rega one would need to use shims for VTA adjustment if not using Rega's line of cartridges.  I personally would never buy an arm without adjustable VTA.  The Project arms, while nothing special, also have low effective mass, so one could use them with high compliance carts (e.g. vintage MM) so there is more room for exploring different carts on the Project.  All that said, I used to have a Project Esprit(?) and it sounded just okay, with bad isolation from itself and the environment.  Moved on to Clearaudio not long after that.