Hi novakom,
I would echo the great advice and comments that Lew provided.
Buckling column gel is a much more costly material that Bob’s wouldn’t use in their mattresses. The mattress you linked is a combination of an innerspring with memory foam and polyfoam layers on top of it (although they don’t provide any information about the quality of their foam layers). The “gel” they are referring to is a type of gel that is added to memory foam and this gel memory foam is only a 1/4" layer (as Lew mentioned it’s basically meaningless and just there for label copy). Their innerspring mattresses are made by King Koil although as you can see here … the employees there know little about their mattresses.
No … the gel is only a 1/4" layer of memory foam and would have almost no effect on the feel or performance of the mattress.
I would advise against this except as a last resort and unless you are familiar with mattress materials and construction because if you remove the Eurotop and don’t replace it with something else that is suitable you will have a much firmer mattress than you already have (the eurotop makes it softer not firmer).
I’m not so sure that the mattress is a “train wreck” although the odds are good that the materials in the upper layers are lower quality than they should be. The quality of a mattress is very different from how a mattress feels and feel is very subjective. A mattress that works well for one person may be completely unsuitable for the next person in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) depending on their body type, sleeping positions, and sensitivities. I think that the mattress is just firmer than you would prefer but it may be perfect for someone else (even though it may not stay perfect because of the lower quality materials that are in the top layers of the mattress).
As Lew mentioned … a topper is not a good idea on a mattress that is sagging because the topper will just follow the sags and soft spots. It’s not really possible to “fix” a mattress that either was too soft originally or has become that way and has dips and soft spots but there are a few suggestions in post #4 here that may help either partially or temporarily and you can see that Lew also used a similar concept under his mattress to improve the support from under the mattress (instead of using a topper on top of it).
You may be better off to start all over again if your mattress is that unsuitable for your needs and preferences but Lew’s suggestion to add a topper was also a good one because it can add more softness to your comfort layers and help with the durability and slow down the softening of the layers below it. You can find some topper guidelines in post #2 here and the posts it links to.
Both the queen and king size of the Seven Comforts appears to be currently available on their own site here.
Phoenix