TT and phono preamp - what best match for my system

If you can make the reach, I agree with @ghdprentice concerning the P8/Apheta.  You will get good sound with the P6, great sound that you will not likely outgrow with the P8.  The Parasound and REL stuff is all good.

OP, 

FIrst, so many audiophiles swear by vinyl because for most of the last seventy years it was true. Only over the last ten years has digital eclipsed vinyl. First at fairly levels (like $20K / component) then moving up and down the tiers until in most categories digital sound better for roughly the same money. 

It is only over the last ten years it became obvious the sound of analog or digital is in the components you use to play them back and not innate in the media itself. So now you can put together a system where the digital is warmer and more natural sounding than the analog and analog is more detailed and fatiguing. 

While a long while back vinyl was more detailed, it was primarily loved for its natural sound more so than  detail. The advent of the CD out did vinyl in most systems at midlevel and budget system on bass, noise floor and detail. But it was not natural sounding... at all.

I have a very good digital and analog leg in my main system and they sound virtually identical. This is because I chose the components for musical and natural presentation... as if I was in the concert hall. There is more variation in vinyl because they depend on how close to the first pressing was on the stamper... the first ones off sound much better than the 1,000th or 2,000th. So there is more variation. Then you have cleaning to make sure they are clean. Then you have vinyl noise floor. Until you get to around  $2.5K cartridge that doesn’t disappear A friend of mine who listens to vinyl extensively and has for decades and called me recently really shocked that with his new $2.5K cartridge the noise floor just dropped away. He had not idea that was possible as he had been using  $500~$1K cartridges for year. I bought my first +$2.5K (this is an approximation) about thirty years ago, my mouth dropped open, I could not believe it was possible... exactly the same reaction my friend had. 

As far as the Rega. The table arm and cartridge are made for each other. They are not overly analytical sounding... which with would complement your system. I personally am not a Rega fan, but I think given your system, it would be the right choice. 

As far as a valid reason to add analog to your system. You like the idea of vinyl... the expense and inconvenience or just for some historic reason. If you want a better sounding system then you want to invest in your digital side. 

The Rega P6 is not a good choice. It’s between the 3 and the 8 and really is just an upgraded 3. The 3 is much better value or save for the P8.

And I love vinyl by the way, a whole lot more than any other media. A trip to memory lane, every single time.

Let’s be clear what the OP is speaking about here. The Planar 6 RS edition jettisons the RB303 arm for the RB808 arm used on the Planar 8, likewise the sub-platter is the all metal device which sports dual drive belts also from the P8.

Does it sound any better than the P6 or as good as the P8? Never having heard one, I have no idea, though I know what it is. And no "RS" does not stand for Radio Shack.

My take is that the P6 appeals to someone looking for a traditional form factor within the Rega line, so this is an attempt to push that performance closer to the P8.

Having worked in the industry for well over 20 years, I can say that my personal preference, sonically - and a personal preference it is - is for a phonograph over a digital source, YMMV.

The Technics 1200G at $5K is a better turntable than the Rega.