Hi great southern land … and welcome from north of the equator to south of the equator :),
In general terms you are wise to avoid pillowtops … especially in the major brands. Most of the time a pillowtop is made up of lower quality and unneccessary soft polyfoam or synthetic fibers which are on top of even more layers of polyfoam in the main mattress. These “extra layers” are there to cater to the consumer belief that thicker is better. Because of the amount of lower quality materials in the top of the mattress which tends to soften and break down more quickly than higher quality materials … these types of mattresses more than any other are the source of the problem many people have with foam softening, body impressions, and hills and valleys in the mattress (valleys where you sleep and hills in between two sleepers). These hills and valleys are an even bigger problem with the larger mattress sizes that use lower quality materials that can’t be flipped (which is the ideal), or that can’t be turned 1/4 turn during regular maintenance (like a regular king size) because they are not “square enough” (such as a queen size or a california king size) or because they are zoned from head to foot and not sideways.
Part of this is because of the type of materials used in the pillowtops (materials that are more prone to softening) and part of this is because of the addition of too much foam than is appropriate for the material. There are also a lot of “fake” pillowtops which is a construction which is made to look like a pillowtop (because people believe it is a good thing or that it looks like a “quality” mattress) but is not a true pillowtop in the sense that the foam in the pillowtop isn’t fully surrounded by material which allows it to act more independently. Another issue is that some mattresses don’t have the pillowtop look or construction (a separate topper attached to the mattress) but still have way too much lower quality material in the top part of the mattress.
This also relates to your husbands heat issues. Some foam will sleep hotter than others because they are more insulating (breathe less) and because they allow you to sink in deeper into the mattress which will surround you with more of the insulating foam. Memory foam will allow you to sink in the deepest and while there are degrees of breathability in memory foam … in general they are the least breathable and so the “hottest” of the three types of foam. Polyfoam is next in line in terms of breathability while latex is the most breathable of the foams. Of the two types of latex (Dunlop and Talalay) … talalay is the most breathable. So the type and breathability of the foam in your mattress and how deeply you sink into it is just as important as whether it is an actual pillowtop.
There is also a wide variety of different materials that are used in the quilting and ticking layers of a mattress which can either add to or detract from how hot a mattress sleeps. In general, natural fibers in the quilting layers and in the ticking itself are more breathable than synthetic materials. This is one of the reasons many people have wool quilting in their mattress or add a wool mattress pad on top of their mattress. The bedding you use can also make a significant difference to how hot you sleep with natural fibers being generally cooler than synthetic fibers.
There are also 3 main “cooling technologies” that are used in mattresses which are talked about in post #4 here. The most important of these IMO is ventilation and humidity control.
So how hot someone sleeps … besides being a function of their own body metabolism and makeup … will be influenced by how deeply they sink into the mattress … the type of materials they are sinking into (how insulating they are) … the quilting and ticking of the mattress … the type and combinations of “cooling technologies” that are used … and the type of bedding that goes over the mattress (mattress protector, mattress pads, sheets, and blankets). Combinations of different methods will always work better than any one alone.
The coolest mattress of all is an innerspring mattress with natural fibers in the padding above and below the springs (no foam at all) but these can be expensive if they are well made (natural fibers are more expensive and more difficult to work with than foam and especially inexpensive foam) and are also not the most comfortable for many people. For most people … higher quality more breathable foams and good construction methods in appropriate thicknesses and levels of firmness and with cooler more breathable materials in the quilting, ticking, and bedding are fine even for hot sleepers.
My thoughts about Ikea would depend on which specific mattress you were talking about. As a whole Ikea has mixed reviews as some of their stuff is low quality and some is higher quality and better value. Some of their memory foam mattresses for example use 3 lb memory foam which I would stay away from completely. Some of the support layers in their mattresses use 1.5 lb polyfoam which is a lower quality and cheaper material than is usually used in a support layer. Many of their mattresses don’t have the specs necessary to really tell the quality and their customer support is not very knowledgeable in these areas so in these cases you would be buying an unknown. Some of their mattresses do have good value (such as the ones that use mostly natural dunlop latex) although even here they are not using the highest quality material available.
As long as you are focused on the materials in a specific mattress and avoid buying “unknown materials” or low quality materials … then you would usually be fine and you could find some better value at Ikea mixed in with the lower quality products.