I'm quite interested to hear the three Piano Concertos. They look like quite substantial works.
They are. Despite what initial impressions of what you hear might suggest, expect Beethoven rather than Rachmaninov in how the music is organized and presented and you'll be OK in delving into the Medtnerian world.
Recommendations:
First Concerto: Zhukov, Alexeev, Sudbin, Tozer
Second Concerto: Demidenko and Sudbin
Third Concerto: Demidenko, Ponti and Sudbin
For the Zhukov, look further up in the thread for some youtube links. Madge's set is also interesting, if you happen to find it cheaply. The Tozer set is recommended, but not as a first foray into the works (he plays beautifully, but his fire is generally very subdued). Don't you even come near the Scherbakov recordings on Naxos.
If you haven't already, read the thread for further suggestions and reviews.