Nothing wrong with that... I have 48 of each gaunt (horm and spine) myself. Usually they wouldn't all make it out until over 2k (most, but not all), but it's fun (and I don't run a "swarm" list... I try to balance it out). You can definitely fit them in if you want.
I usually run 32 horms (2 broods) and 24 spines (1 brood)... although I'm trying to add in a 2nd brood of spines thanks to their great holding ability (and shielding, for that matter). I use spinegaunts as objective holders and swamp units. Shooting is generally an extra benefit if it happens. Termagaunts are fine if you choose, but you have to make use of that gun that you pay for. If you don't plan to actively try to shoot with them, you may as well go for Spines for the lower cost, same CC ability, and all that.
Khira'lyth