A friendly hello

Welcome. I think the best thing you can do is try out a couple of models from the loaner program and decide what you like best.

I use the Reflex M + PSU myself but don't use Rega cartridges. I'm sure someone else here has though. You will find that a wide variety of cartridge brands and types are used with GS phono preamps.

I have the Reflex M with PSU1 and using it with an Ortofon 2m Bronze cart. My amp does not come with Phono amp or headphone amp built in which is fine by me, but my last amp did and I found the SE2 a great improvement over the built in one, Some reviewer said that the amps phono amp was vary good but the SE2 just blow it away (I got the up grade bug hence the Reflex) I think you are doing your system a disservice by saying it's not audiophile your RP6 alone is a great turntable, not familiar with the rest of your system.

Try the loaner program it's a great way of hearing it for your self in your system and room. 

I used the loan scheme to try the Reflex M a year ago when I had a Rega Planar3 with Nag cartridge. I was blown away by the improvement in sound quality and detail over the mid range Pro***t phono stage I had been using. I was ready to go for one when I realised after discussing with John C that the Accession M would give me the flexibility for 'ripping' that I wanted.  So I ended buying a nearly new Acc.

Just a word of warning, once you hear the improvement the GS phono stage gives, you'll want to test more GS equipment, it's addictive!