I have played the Valved Promaster and the Easy Reeder from Suzuki.
The Easy Reeder is very cheap (about $5 - $6) and comes, I think, only in C and has ugly red anodized covers, but it's quite a decent little harp. Stays in tune, and with a little adjustment, overblows quite well. You won't get a BIG sound out of it, but for a cheap Special 20 knockoff it's quite passable.
The Valved ProMaster, for me, is no substitute for a MeisterKlasse - it doesn't have that thick-walled Cadillac engine feel. I always feel with a MeisterKlasse that there are playing possibilities beyond the reach of human stamina, and that they can actually be worn in over several years, like a very good pair of shoes. I can drive them harder, and get more volume out of them, than any stock harp I've ever played (I'm leaving Joe Filisko's custom jobs out of the discussion). Of course, I'm talking about the pre-modular instruments.
The valves on the valved ProMaster make the blow chord very loud, as they prevent any of the blow air from escaping through the draw reeds (and also prevent overblowing, although I've been told that the unvalved version overblows well). They make it possible to bend the blow notes in the first six holes, but not with ease or control you might hope for. But at least you can get more vibrato, and do some expressive bending on the blow notes. These are nice capabilities, and create a certain niche for this instrument.
However, the valves also buzz quite a bit after some playing. I'm a medium hard player, and I found that the buzzing set in after a couple of months of keeping this harp in my general rotation of instruments. It also went out of tune a bit. This is to be expected, but Suzuki's advertising tends to sell the in-tune aspect a little too much.
I've never played the Leghorn chromatic, but I'm told it's the same as the Huang 1248. Depending on who tells the tale, Huang gets all the good ones and leaves the rest to Suzuki, or the other way around. Heaven knows who's right.
Spence Pearson asks about taking the round-hole mouthpiece from a Leghorn and putting it on a Hohner 270. I can't say anything about this, but I know it works with a 270 and a 12-hole Hering. Only problem is, you also have to migrate the screws that hold the mouthpiece down, and these may be a different thickness from those on your Hohner, and either be too small for the screw hole - which is in wood - and fall out, or be too large and ruin the hole if you decide to go back to the regular 270 mouthpiece.
One thing I observed when I migrated the mouthpieces was that the response and some of the tone (brightness, warmth and size) - both good and bad aspects - tended to migrate along with the mouthpiece.
As far as 16-hole chromatics go, the Larry Adler 16-holer is just a 280 with different covers and box, while the 12-hole Larry Adler is just a 270 - this from Gerhard Mueller, Hohner production manager.
I haven't played a 280 for several years, and the last one I bought, in 1971, I didn't like (just before that, I lost a Larry Adler which was one of the best 64's I ever owned. I mentioned this to Gerhard Mueller. He commented, "maybe the guy on the production line was having a good day when he made it."). The Super 64 is a nice instrument, if you can get one that doesn't leak like a sieve. The Super 64X is the 16-hole instrument for my money - big sound, good action, airtight. Many people mourn the CBH 2016, no longer made by Hohner (Cham-Ber Huang, the reputed inventor, has some interesting comments on this in the forthcoming HIP No. 5), but people want a fortune for these nowadays, and I always found them plasticky sounding when miked, and plagued by valve problems.
I've never played an Amadeus, but I stood next to Cham-Ber Haung when he tried one, and he didn't seem overly impressed. The August-September 1992 issue of Harmonica World (put out by the National Harmonica League in Britain) contains a review by British chromatic maven Douglas Tate, who has recently published a book on chromatic repair and care. After over 100 hours of playing the Amadeus, he concludes that "in spite of some quite serious flaws, it is a brilliant instrument." He likens it to a good quality student flute, and notes that his review instruments (he received two) had matured over time. This is quite high praise from a man who built his own stainless steel chromatic in 1967 and has played nothing else since. He spends most of the review commenting on the construction, then goes on to describe its musical qualities, saying that it is "quite wonderful to play."
If you want to get the issue containing the review, you could contact HW's editor, Steve Jennings, who is on this list and can be reached directly at 100010.11~ompuserve.com