Going lower usually is not an option- while it is possible, you must allow for venting of LP, and moving the outside access door is a magnitude more difficult, plus the issues of service.
The only problem with going up is the doors- if you remove the old refrigerator and look at the cross piece at the top, you will likely see it is removable, pocket screwed from the back. If it isn't, it will be stapled- just pull the staples. After removing it is fairly easy to move the floor of the cabinet up.
You might even find there is a filler piece to the side- usually refrigerator openings under 23.x inches wide use a side filler piece as well.