@milpai - thanks for the kind words.
Most class D amps are built with a switch mode power supply because they are a lot cheaper, lighter and smaller, so the overall amp can be a lot less expensive for a given power output. Modern class D amps have lots of negative feedback, so the power supply rejection ratio is quite high and with the simple distortion measurements that are typically used, they measure just fine. But that doesn't mean they are going to sound as good.
Over the years (45 yrs as an audio enthusiast) I have found that a good power supply with plenty of current reserves has more impact on the sound quality than perhaps anything else in an audio circuit.
A large linear power supply can provide much more current reserves and not introduce lots of high frequency noise that has to be filtered out or removed using feedback. I have not A/B compared a SMPS supply against a large linear supply with the Purifi module, but almost all high-end amps, including class D amps, use a linear supply.
On top of all that, I wanted to add my personal touch to the amps, and I'm a lot more comfortable building a linear supply than trying my hand at an SMPS. I didn't want to just drop a pre-assembled module in the box.
And I'm quite happy with the way it sounds. I'm not sure how much of that was from the linear supply, but I don't think it can hurt (except the wallet).
Regarding driving a 2 ohm load, class D amps have exceptionally low output impedance, and can easily handle a low impedance load. The only limitation is the maximum current. The lower the load impedance, the lower the efficiency the amp will operate, so at some point the amp will protect itself and prevent thermal overload (generally controlled by maximum current). The Purifi module is rated at 25A peaks which is more than enough to hit 800w or more into 2ohms (which is where the amp will voltage clip). It can't sustain this for long due to thermal limitations, but you don't need that unless you have very inefficient speakers.
So it really depends on how much power is required by your speakers. My speakers are nominally 92db/w efficiency and I have to crank the heck out of them to come anywhere near clipping. I have a peak reading LED power meter on my amps with 32 segments measuring 1db increments. With all 32 segments lit, the amp is close to clipping (50v pk-pk). Most of the time I'm listening, I am barely blipping the second LED (approximately 0.3w).
