Mastersound 845PSE monoblocks: The trouble with Parallel Single Ended amplifier designs is they don't perform as well as a Single Ended Triode design with a single output valve per channel. The problem is that 2 output valves in parallel are not electrically identical, so each valve will amplify the signal slightly differently. You can correct this to some extent by applying some feedback, but that makes a mockery of using a single ended triode design in the first place. I suspect this is not done in the Mastersound, but relies on the matching of each pair of output valves. Paralleling output valves also reduces the audio performance considerably. The best results are achieved using a single triode output valve per channel.
Ming Da 805 monoblocks: This design is Class A2 and not a proper Class A design. You can achieve more power from Class A2, hence the "quoted" 45 watt spec, but I bet when you measure them into a real load they won't produce anything like 45 watts
, or if they do it will be at something like 10-20% distortion. Class A2 amplifiers do not sound anywhere near as good as Class A amplifiers. You can tell Class A2 amplifiers by the extra power tube required (6L6 in this case) to drive the 805 valve. A good proper Class A SET design should be able to consist of a driver valve driving the triode power output valve, so just 2 stages. Done correctly with 2 stages and 2 valves per channel and interstage transformer coupled, it really doesn't get any better than this, especially into some high efficiency speakers like the Cornwalls....