So much goes into deciding what will be the best diet for your horse. It's nice to see so many people that are actually doing the research needed to properly feed their animals. :)
I'll be honest - it took me quite some time to figure out what was the best diet for my OTTB. My first horse was an appy mare who I swear would plump out just LOOKING at food (of any kind). She would maintain a lovely weight/condition on just orchard grass/alfalfa mix alone. Then I got my TB and hay alone just does not cut it. It doesn't matter how much hay you give him (free choice even and good quality) he still will not maintain weight/condition as he should. So I did research and picked as many people's brains as I could to come up with a plan. At this point - to keep him in just good condition (as in not show/performance condition) he gets orchard grass/alfalfa mix hay (~28lbs/day), 5lbs of strategy healthy edge (the higher fat concentration in this formula compared to the regular strategy makes a HUGE difference in both his condition and mental state), 5 lbs of a stable mix locally milled (Elk Grove Milling Product Line | Stable Mix
) plus his supplements (probios, u-guard, glucosamine, msm, and electrolytes).
I honestly never imagined i'd have a horse that had such specific dietary needs - but i'm glad I spent the time to learn what I could and made the best choices for him. To the op, sounds like you'll do the same for your horse. ;)