Using a single block doesn't double your pulling power. This is a common perpetuated misconception. You redirect force with a single block.
https://sciencing.com/how-to-use-a-single-and-double-pulley-system-13415028.html
I'd totally agree on that point. I just think that personally, I would either save up to run the higher quality Warn line I previously mentioned, or just be happy running the HF winch (which I do, without issue).
Let's be honest here though, that extended warranty covers the whole winch for either three to five years. The Warn doesn't come close to that warranty.
I love the Warn M, or XD series of winches, and think they're worth every penny. Their "introductory" line isn't better than the HF winches...