Knghifi, the Phillips 5R4GYS was rather grainy and had too much sibilence in the PS 9.0. Imaging was not as good as the 1944 vintage Westinghouse, which BTW was the last one Brent Jesse had. The Phillips is a very good tube in the PS 9.9, but not a very good tube in the 9.0. I've only had it for a week, so it may change with a few more hours.
I found some RCA voltage regulators but am still looking for Sylvanias.