Home warranties come in all shapes, sizes, coverages and prices. I found this review page and thought you might be interested in seeing how other home owners review home warranties. Take a look at the Reviews of Home Warranties and let me know if you need help in any way.
Be sure to note that the #1 rated warranty is Allied Warranty, and note the covereage for septic systems that can be added.
The next best rating for a warranty company in Texas is BFS Home Warranty. Unfortunately their web site is extremely limited... consumers review it highly though.