My Knighty did fair well using Amp-b. However, there are several additions to that. First of all, I've been told that amp-b + itra is good for breaking the high fever that often comes with the onset of acute symptoms.
I don't think anyone would argue that Itra takes a while to build up an effective dose in the blood to start killing off yeasts. Amp-b, being an IV drug starts at the time of administration. I've also been told that both drugs together have a synergistic effect. Two pronged attack, so to speak. Also with the addition of Itra, a lesser amount of Amp-B can be used. Amp-b is metabolized by the kidneys, Itra by the liver, so that's in our favor too.
Our routine was to deliver amp-b every other day, and then on alternate days, test for kidney functions. Testing must be done, regularly, consistently and constantly. We ran this therapy for about 7 doses of amp-b, on a schedule of 10 doses. A full dose therapy of amp-b would have been more like 20 doses.
Knighty's fever broke after about 2 weeks and the amp-b treatments were beginning to show. The IV had slipped out of the vein and a large bolus of saline+amp-b was deposited under his front leg's skin. It ulcerated and was pretty ugly for a long time.
I can't say if amp-b would work in your situation. I do think it's a good and valuable therapy for dogs late along the diagnosis curve and close to, well, you know what happens to late Dx'ed dogs. Knighty was a very strong and healthy dog when this happened, he didn't have any other health issues, he had lots of mental and physical reserves. I think this is probably what helped him as much as anything.
You've got a complex situation. Talk to your vet. Bring up Amp-b and see what they say. Thinking it's a miracle or ruling it out off hand, based on a few anecdotal comments is probably not the way to go. Get a real, live vet's opinion. Itra is no doubt preferred. It is tolerated better, but it's no easy thing either. A dog's underlying health issues, age, fitness and probably tons of other things should be dictating what therapy is right for you.
I can tell you that a coworker was treated with Amp-b+Itra for blasto just a few years ago. I think it was 5 years ago in Marquette Michigan. So I can't see how Amp-b should be lumped in with leeches and other medieval medical practices. (Although in the U.P. that might be cutting edge!

)
It's my opinion that amp-b is not necessarily worse than Itra at all. Both drugs are harsh should be given respect. The long and high dose of Itra flaked out Knighty's Liver enzyme numbers for the rest of his life. They never really totally rebounded to the "normal" range. Let's face it, If we were fighting cancer, these drugs would be called "chemotherapy". Hell, they are chemical therapies, therefore they are chemotherapy, just for something else besides cancer. Sometimes I think that we all think of Itra and a benign miracle drug. Yes, it does save plenty of dogs (humans too probably) and the result of not taking it is certain death, so just about any side effects are considered "good". Yet every other post here is "how do I get my dog to eat during itra therapy?" We can all list off plenty of crappy side effects for all these drugs.
Wish I had a better answer for you than all that crud above.
Kash