I currently have a ARC ph-5 phono stage

Yes the PH-6 is a nice improvement from the PH-5. I own the PH-6 and a friend owns the PH-5. We have compared them side-by-side.

The PH-6 provides a much smoother, more refined sound versus the PH-5 with a deeper and better articulated soundstage. Lower noise floor, blacker background.

The PH-5 is a great phono stage. ARC has raised the bar considerably with the PH-6.

Anyone compare the PH-7 to the PH-6 or PH-8?

Why not just take your PH5 to the dealer who claims the PH6 is "smoother" and hear the two for yourself?

I was checking a year ago or so the PH5 and I liked a lot his sound, transparent, fast, dynamic, sweet and airy but I found a bass problem imho his bass articulation and extension was a bit raquitic in comparation with similar price phono preamps.

You need a deep bass cartridge like Benz Micros, Koetsus, etc... .

The PH5 is one of the best phono preamps I ever heard. Enjoy it and if you want to produce a change you should try another brand.