Vandersteen 5A vs Martin Logan Prodigy

I have not owned either, but have listened to both quite a bit in the past.
Even though the 5As have the active 400 watt bass amplifier to handle the bottom end, your 50 watts of SET power may not go as far as they need too.
The Prodigies are 91db sensitive VS 87db for the 5As. Of course there are quite a few variables, room size, room composition, listening level and the type of music you listen to.
Electrostatics will always have that seductive "air" that other speakers can't touch.
The 5As ( when properly dialed in ) will have room/bass integration and coherence as good as or better than any electrostatic and will completely blow you away.
For what its worth, my local Vandersteen dealer felt that 60 watts of OTL wasn't enough for his personal 5As.
If you are happy with the sound that you have now, roll with it.
If you have an itch to experiment, you may need a more powerful tube amp to reach audio nirvana with the 5As, but it will have been worth it.
I went from ESLs to Horns.

I do own 5As, bought this summer. I drove them initially with 160Watts-into-8/320-into-4 Monarchy Audio SE-160s. Before I bought the 5As, I had performed some some minor improvements to the amps including installing a switchable 85Hz hi-pass filter. The combination of 160s and 5As sounded EXCELLENT, but, being a long-time lots-of-vacuumtubes guy, I got the itch again. This time it was for OTL amps, and I brought home a pair of Atma-Sphere M-60Mk3.1s. I expect these are the '60 watts of OTL' power mentioned above.

My system with the M-60s sounds even better--cleaner, more transparent--than it ever has, and the system does NOT lack dynamnics. I'm no headbanging dideebopper, but I do listen to large-orchestra music quite loudly sometimes. Unless you have a VERY-large room and listen quite loudly, I believe your 50-Watt Carys will sound quite good with the 5As, recognising that you'll use a 100Hz hi-pass filter with them.

The 5As are the most natural, nonfatiguing, cohesive, MUSICAL-sounding speakers I've ever heard. Go for them!
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You are comparing apples with oranges - both are excellent speakers, happy owners of Prodigy's will also say "they are the most natural, nonfatiguing, cohesive, MUSICAL-sounding speakers I've ever heard. Keep them!

I have owned Prodigy's in the past and moved to Soundlab's A1 PX. May be the Vandersteen will have better bass frequencies, and can handle heavy rock better than the ML's, but my preference would still go for the Prodigy. The choice will depend on owner preferences and room acoustics.

BTW, did you ever heard the Prodigy's with the Descent subwoofer? It takes them to a new world.

The Cary 805 Ae Monos 8 Ohm taps Kimber Kable Select with the Vandersteen 5As are to die for.
We used this combo at one of the stereophile NY shows with 26 folks in the room .
After playing Bach toccata in fugue with this combo applause prevailed.
Try also Vivaldi Fabio Biondi 4 seasons listen to the size and clarity of wood instruments and articulation of the strings without any smearing I think you will enjoy.
Best Johnnyr