Is it easier to sell mono blocks or stereo amp on the used market?

I might ask how committed you are to the decision of buying the new amps, if your first concern is how easy will they be to sell.  I say buy what you think you will enjoy the most right now.  Who knows, you may have them for 10 years and the resale question is moot.  IMHO.  Cheers.

+1, “buy what you think you will enjoy the most right now”. And also what amplifier sounds the best to you.

Two mono block amps or a single stereo amp decision depends on what sounds best to you in your home audio system. Concern about space also needs to be considered (one box or two). In my case, I decided on an integrated amp.

In summary, “The decision between two monoblock amplifiers and a single stereo amplifier depends on your specific needs and preferences:
    •    Sound Quality: Monoblocks offer better channel separation and reduced crosstalk, ideal for high-end systems. However, modern stereo amps often have negligible interference, making the difference minimal for most users.
    •    Power Needs: Monoblocks generally provide higher power output, suitable for demanding speakers.
    •    Space and Cost: Stereo amps are more compact and cost-effective, while monoblocks require more space and are pricier per channel.
    •    Practicality: Stereo amps simplify setup, while monoblocks allow flexibility in placement and shorter speaker cables”. 

If you are primarily concerned with sound quality, then monoblocks would be the choice. For me, that would be the only concern. But, I can't imagine that stereo amps are easier to sell. 

The OP wasn't asking for advice on which to buy but for advice on which would be easier to sell. I'm kind of curious about his question as well.