"I have got about 150 classical LPs.....Some of the RCA discs have the Dynagroove system..."

Er, well - typically only if they were the US releases.
Decca stopped importing Dynagroove stampers after just a few years
(c.'65/6) - even though 'Dynagoove' was still emblazoned on the
sleeves/labels thereafter (and until RCA set up their own UK factory
in Washington, Durham in about 1969. AFAIK RCA UK didn't utilize the
system - also they re-cut back-catalogue titles, but sleeves weren't
amended/old stocks used).
In other words, there are not too many genuine Dynagoove's pressed in
the UK.
They can be pretty 'dynamic' - but it wasn't really RCA's best
recording period.
For a good classical original RCA/Decca-pressed Dynagroove, Ravel:
Daphnis et Chloe / Roussel: Bacchus et Ariadne, 2nd Suites - (Chicago
SO/Jean Martinon) - takes some beating.