Hi meyerba,
Thanks for letting us know what you ended up deciding … and congratulations on your new mattress 
If you are comfortable with a floor model purchase then it certainly seems like good value to me!
Your mattress is a latex/polyfoam hybrid and has a polyfoam support core rather than latex so the criteria for a suitable foundation would be a little different than an all latex mattress. In most cases … the most suitable foundation or support surface for a foam mattress is one that is rigid and non flexing and has an evenly supportive surface. The Ikea Sultan Luroy slats are flexible and not rigid so they would change how the mattress feels because they have some flex to them and would be a more “active” part of your sleeping system. As far as I know the Ikea beds also don’t have any center support to the floor (only an unsupported metal center beam) so I would see if there is a way that you can add this as well.
I would only do this if there were no other suitable options available to you and you were comfortable with the additional risk that can be part of a solid support surface (see post #10 here).
Phoenix