I think you'll be happy with 20: virtually all your countertop appliances will fit in that space, and the only thing you'll gain mby going higher is making it harder to reach stuff on the top shelf.

You can use the above cab space to display things, maybe add some plants or ambiant lighting.

I could be wrong, but I think standard is 18" off the counter. I also read an article (someone here might have provided the link) that recommended lowering the standard to 15" to make it more reachable; but I guess a lot depends on your height (I am short.)

Minimum height is determined by the following:

• Height of countertop material (usually 1-1/2" or so)

Height of tallest small appliance you will be using on the counter + 1/4" [Even if it isn't stored on the counter, you still need room to maneuver it while using it]
Height of light rail (usually 1" or more...mine is 1-3/8"). If you don't know the height of your light rail, use 1-1/2" as the height.

Add these three measurements together and this is the minimum distance your wall cabinets should be mounted above your base cabinets (without countertop)

If the countertop is already installed, then only add the last two and measure from your countertop.

HTH!

Wider - I am short and initially it was strange but I love it - the extra few inches you will not notice later on and it's nice for mixers, toaster (to give it room to breath), a 19 inch tv, etc and if you have a small kitchen (given where you live) like us, it makes it look less closed in.

Thanks so much for your speedy help! Now that I've gotten over my initial surprise, I think we'll probably leave the cabinets where they are, per the consensus advice here. I might put a shorter cabinet over the sink though, to give my tall Franke manor house faucet some air.