I can't imagine buying a guitar simply for how loud it is, without regard to the character of its tone. Also, a guitar which is very loud up close may not project as well as some other guitar that carries the sound farther back. For instance, large bodied Maple/Sitka (or Adirondack) guitars project really well and cut through the noise... but I don't like the bright tone and the strong fundamental sound with minimal overtones. But that is just me, my style, and my ears.
I think the first step in choosing your Taylor BTO is to chose a body shape. That will have the single biggest impact on the overall sound. A Grand Symphony (GS), Dreadnought (DN), or the new Grand Orchestra (GO) will be louder than a Grand Auditorium (GA) or Grand Concert (GC) because the larger guitars have more surface area to their tops and more space inside the body, so they can move more air when the strings vibrate. The various Taylor body styles all have different tone characters, as well, and will shape the overall sound of the guitar with whatever woods you choose.
Adirondack is generally considered to have the highest amount of maximum volume, but Sitka is close enough that the variance between pieces of wood can make up that difference sometimes. According to Bob Taylor it is more important to upgrade to Adirondack CV bracing, because of it's spring-like properties, than whether you choose Sitka or Adirondack for the top. I suppose Adi for the top and braces would be the ultimate in loudness for any given body style or back/sides wood choice. I wouldn't think of Englemann as the loudest spruce, but it is the one I prefer for the sweeter and warmer tone it gives. But then I don't play with a flat pick. I play fingerstyle and when I do strum, I use the back of my fingernails. Personally, I prefer Cedar tops in general for my technique. It does not have anywhere near the headroom of the woods you are considering, but it will respond the best and be the loudest with a soft touch than the woods in your poll. It will be the quietest in terms of maximum volume at its limit when played hard.
Certainly EIR back & sides would give you a classic tone that everyone is familiar with and emphasizes lows and highs while adding lots of overtones. Mahogany is a familiar sound too and will emphasize the mids with a drier and woodier tone. I described Maple with Spruce in the beginning of this post and that certainly rounds out the most common guitar woods for back/sides. I'll suggest Walnut (my personal favorite) to get the strong lows of EIR with fewer overtones, the present mids and woody tone of Mahogany, and some of the projection of Maple along with its bright zing in the trebles but with more overtones than Maple.
Ultimately you'll have to decide what your needs, priorities, and preferences are based on where and how you play and your own ears. There are few things more fun than designing your Taylor BTO! Good luck and keep us posted on your ultimate choices.
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