Did you buy them from the company in Texas yourself of are you paying your dealer for them? That will determine if you pay sales tax or not.
Of course your home state will ask if you bought anything from out of state when you file your taxes next year and it will be up to you to be honest about those silencers that you didn't want to pay sales tax on...
"No, it's not a silencer. This little doodad is my own invention. I call it a loudener." --Sledge Hammer