Hi checkenlegs,
The CombiZone you linked to is three zones, with one gauge thicker steel in the middle third. This would allow for a bit “firmer” deep down support in the middle third of your body, which is where you probably have a considerable concentration of mass from your training. Being deep down, it’s not something that you would notice so much as you would if you were choosing upper foam comfort layers that were also zoned.
The Quantum Edge system is a newer offering from Leggett and Platt (and separate from the zoning), and it is a very nice edge reinforcement system that replaces the usual solid polyfoam edge systems used by most mattress companies. I personally like edge systems such as this.
For a support core, I wouldn’t have a concern using an item like this. I certainly wouldn’t hesitate to phone Arizona Premium Mattress (mattresses.net - a member here, which means that I think highly of them) and mention any concerns that you have and also talk to them about what you’re trying to accomplish, as they are experienced with helping many mattress DIYers.
If you’re looking at a few other innerspring options, you could look at Texas Pocket Springs or HSM listed in the spring section of the component post here. I would find these options much more desirable than an imported Chinese spring unit or a basic Simmons Recharge spring unit.
Phoenix