gardenspuds,

Here's my personal experience with mattresses.

I had a spring mattress and now have a latex mattress.

One spring mattress was in a CalKing platform (no foundation), it was Ok.
Then, we bought another spring mattress (RestWell) on a box spring foundation. We had problems with the mattress after 7 years, and the company picked it up and returned it without charge.
We had to have a bed while this was being fixed, so we bought an Essentia pure latex mattress, which can be either placed on a box spring foundation or a platform.

My wife and I both prefer this pure latex mattress, and haven't even opened up the repaired mattress mentioned above. I should say that we are using the box springs used for the repaired mattress (we have sinced ordered higher box springs, to replace the 4' box springs that we purchased with the repaired mattress).
After saying all of that, I think your problem may be with the foundation you are reluctent to get rid of, and to further confuse you with which mattress with what foundation.
If you can, I would recommend the mattress that we bought from Essentia (made in Canada).

Good luck!

Here is a link that might be useful: Essentia Mattresses

Thanks for the recommendation, but right now I cannot afford a new mattress system, and I am quite sure the mattress we have is okay, I just don't like the European slat adjustable foundation. One idea I have is to get a new foundation (either box spring or wood slat that is not adjustable foundation), but I'm not sure which would work better with our mattress. This mattress has coils on the bottom layer (don't know how deep, maybe 8 to 10 inches), 2" latex on top of that coils and on top of that, several layers of organic wool and cotton padding.

Thanks.
Barbara