As RevJim says;

Personally I would recommend getting a 26" 4-wheeler spinner case. This will give you the most flexibility for the future (sure you think you're doing a one-off trip, but how about in a year from now).

See how much you can pack into the 26" case, then buy another cheaper larger (28") one to fit all the leftover stuff.

You then end up with;

And finally you're right about the 4-piece luggage sets you can buy for $100 - I don't think they're good value (sure they're cheap, but not 'value').