HDX2 is fine to stack with Gaspari's Thyrotabs. I take it your starting a cutting cycle?
If you are looking into using Gaspari's thyrotabs, you might look into stacking with SAN thyrocuts II. The two products essentially work with eachother for a much more pronounced effect.
There's a whole thread about this on another forum (lean bulk), if you'd like to do some more reading on this protocol. (search: thyroid protocol).