Have you checked with Cary? I don't know why any particular 2a3 would not work in their amp. Monoplate RCAs, Cunninghams, etc. are fantastic tubes, but, these days they are quite pricey. If you have some monoplates, you could try them in the amp with the bias set lower than Cary's recommendation to run the tubes consevatively (I believe Cary biases 2a3s at 70mA, you could try 60mA).
I personally like EML meshplate 2a3s (in Audionote Kageki amps). They have a much stronger bass and mid-bass response than the double plate RCAs that came with my amp, so the sound is not as lean. I've had them for over a year and they work fine. I know that a lot of people have had reliability problems with EML meshplates. When I lent them to someone who used them in another amp, the amps started to sputter after a few minutes and the tubes started to arc. I suspect that the EMLs have to be biased at a much lower current than most 2a3s. My amp is autobias (cathode biased) which is gentler on tubes, but, then again, with amps like your Cary, you could just set the bias at a lower level.
I personally like EML meshplate 2a3s (in Audionote Kageki amps). They have a much stronger bass and mid-bass response than the double plate RCAs that came with my amp, so the sound is not as lean. I've had them for over a year and they work fine. I know that a lot of people have had reliability problems with EML meshplates. When I lent them to someone who used them in another amp, the amps started to sputter after a few minutes and the tubes started to arc. I suspect that the EMLs have to be biased at a much lower current than most 2a3s. My amp is autobias (cathode biased) which is gentler on tubes, but, then again, with amps like your Cary, you could just set the bias at a lower level.