Hi darter,
If you are thinking of going a 40L I would recommend stepping up to the 60L. Have been there and done it. You always need that extra bit of room, especially if you are known to be thirsty at times.
The engels are a good product, but also have a look at the trailblaza fridges possibly the toughest most reliable fridge/freezers out there, with great personal service and backup.
http://www.norcoast.com.au/
Cheers
Carry