Hi, a few months ago I got to audition the Nagra BPS over at Goodwins Highend Audio in Waltham, MA (near Boston).
I have also auditioned the VPS though I did not have as much time the day I heard that setup -- both are among the best I have ever heard.
The BPS was driving a Clearaudio Stradivarius cartridge mounted on an SME10 turntable. It was one of those listening sessions which was truly thrilling.
I am also very familiar with the Sim Audio Moon LP 5.3 phono stage, Musical Fidelity built in and stand alone units, Rogue Audio built in phono stage in one of their higher level preamps, having heard them many times in auditions and in good friends/family systems in the last few years.
The Nagra phono stages are the only ones I have heard which I like better than my McCormack phono drive, Revision A w/powersupply. They have much more refinement, detail, lovely top, tighter and deeper bass, but still sound open and natural. The Sim Audio phono stages sound hard to me.
I have a Benz Glider M2, an LP12 Valhalla Ittok VII, so you can tell I value a slightly warm open sound.
The Nagra BPS is an amazing little unit. Good luck with your search, Stephanie