Hi vettehigh,
Yes I think it would be a good choice and it’s certainly good value. Sams club only has a 5 lb Aerus topper not a mattress and it’s less common to see than the 4 lb. The other advantage of latex is that it is more supportive than memory foam for the times you sleep on your stomach.
There are quite a few steel foundations and some are better than others. Post #2 here and some of the other posts in the thread has some of the more reasonable foundation options and some comments about them . At one point I was a little skeptical of using some of the lower cost wire grid bases for a latex mattress because of the possibility that the thinner wire grids have less surface area than wooden slats and could let the very elastic latex sink into them but based on the feedback I’ve had from some manufacturers that are using them they seem to work well and with a polyfoam base they would be no problem IMO. They certainly are strong and can support up to 2500 lbs.
Phoenix