First of all, that's a good bike at that price point and you probably wouldn't consider upgrading it unless you enjoyed it.

That being said, I'm not sure that I would invest that much more money in that particular bike. Again, while it is very good for what it is, I think you might be about to head down a path of spending a lot of money trying to make it into something it was never meant to be.

I've been down that path with cars and motorcycles in the past and it is rarely cost effective. Once I upgraded one component, then I would notice how much one or two or three other components also "needed" upgrading to be comparable with the other newly upgraded component. A target of $X often turned into $XX. Upgrade-itis can often wind up being be an expensive malady.

As an alternative, I would recommend perhaps considering the used bike upgrade path. With a little patience, you can probably spend 50% more in six months and get a used bike with a sub 20 frame & wheel combo with with a full 105, Rival, or maybe even Ultegra grouping including the brakes etc...

Anyway, food for thought. Happy Thanksgiving.