I use ChompSMS and it allows you to blacklist texts. Best of my knowledge you'll have to allow the first text to be received, then blacklist that number.
Blacklisting won't refuse/deny the text, but it will not alert you when the text is received and it will hide the conversation list.
There are two options for checking the texts as well:
1) You can re-enable that conversation through options
2) You can make that blacklisted conversation "visible"
By making it visible you still won't get a notification from that number but you can go in and see what they've been sending you.
I hope this helps and I really hope you're happy with your X!
Congrats!