Technology in Class D amps is moving really fast and is already above and beyond class A or AB by a margin.
People always talk about Power (Watt) and the fact that the difference between 500W and 1000W is only a few dB and changes little to the volume, and you don't listen that loud anyway. However, is it not the case that the reason to get an Amp with more Power (Watt) is that it might have more current (Amperes)? And more current is desirable even if you listed at 5 watt. It will provide you all the other advantage (aside from loudness) that people associate with powerful amplifiers: amazing driver control especially in the bottom end, soundstage, authority, etc..
Current (Ampere) of different options:
- The Hypex NC502MP recommended above is 27A. That is the best value for money by far. 27A is a lot, and the cost of Hypex NC502MP is really low for the performance.
- Purifi 1ET400A is around 25A
- Hypex NC1200 is 40A
- Purifi 1ET7040SA is 40A (the latest baby on the street)
- Van Alstine DVA M750 : the current is not mentioned. But I would guess 20-25A (how to guess this is not easy, it is rated 750w @ 8ohm and 1000w @ 4ohm, so I will assume 1250W @ 2 ohm being generous => 1250W/2ohm = 625 = 25A*25A => 25A).
Save yourself big money and go for one of the 40A amp! Or go for Hypex NC502MP (literally 750 usd) and upgrade later (who knows what new tech will bring in 10 years + it is so fun to upgrade).
It is not current you need to provide good "control" of speakers, it is low output impedance. You want the amplifier to be able to hold the output voltage regardless of current into the speaker, or back emf from it.
A high power amp will only deliver its high current at high voltage (ie at high power levels).
Output impedance will typically be lower for higher power amps of the same design, but it also depends on the level of feedback in the design, so it can vary a lot between amps at the same power, or it is possible for the impedance to be lower with a lower power amp than with a higher power amp with less feedback.
The current crop of respected Class D amps (Think Hypex and Purify) are typically very low output impdeance due to using high levels of feedback in the designs.
EDIT:
Also be careful with some of the current ratings you have given above. For example, the NC1200 40A you have given isn't a rated output current- it is a current limit setting - and you've chosend the max value. It could be as low as 34A, and as a current limit, it is a protection level, not an operating level.
Since it is rated 1200W into 2ohm (which will be a current defined rating), the expected operating current can be assumed to be sqrt(1200/2) = 25A. Even at that level, the current has started to limit since that is with clipping at 1%THD.