Another factor to consider is what type of guitar you are trying to amplify, and what kind of pickup is in that geetar.
My Yamaha nylon stringed has a combination under the saddle pickup and gooseneck mic. I use mostly the under the saddle, and it sounds good in almost any amp, with volume to spare. Feedback is rarely an issue. This is what these pickups were designed for.
Now, when I dial in a bit of the mic to get a little bit of warmth, I venture into the land of feedback, so my sound options are limited, as far as how loud I can get. But it still sounds good, like I said, with any amp.
Maybe it's just the nature of the nylon strings, that makes it compatible with any situation, almost.
My F-30R is fitted with a Fishman Rare Earth Blend, and even with the magnetic pickup, combined with the gooseneck mic (like the Yamaha), it takes a bit of effort to get a good sound in almost any amp. I leave the blender dial in the middle, between the mag and the mic, and it takes a bit of tweaking to get a good sound; natural, and pleasing to my ears. I do get the sound I want, it is still the best sound, but it takes a bit of knob turning to get there.
A lot of guys just leave the setting in the magnetic pickup position, and just plug in. That sounds fine for some, you get lots of volume before feedback, but then it sounds like an electric guitar, and a not so very good one.
I gave up on an exclusive under the saddle pickup long ago. Although, they are very practical in most live situations.
Heck, if that is all that I am going to play in, then I would simply get a Line 6 Variac acoustic. A lot of options on that baby - they modeled an assortment of acoustic guitars, one of which was the Guild D-40 - and virtually no feedback problems.
Back to the acoustic; it is best to start with a good source, then tweak from there. Not the other way around. A good friend said to me concerning this: "You can't polish a turd!"
Metalman