Please tutor me on some integrated amp basics.

I’ve recently purchased Magico A3 speakers and a VPI Classic 2 SE turntable with an Ortofon Black 2M moving magnet cartridge. I have a Marantz SA 8005 CD/SACD player to play the few (maybe a hundred or so) CD’s in my possession.
I’ve mostly vinyl albums and no streaming sources. I’m next going to upgrade my old amp/preamp purchased back in the late 70’s with a new, probably integrated, one and am starting to do some research.

Here’s where I need some tutoring. A lot has changed since the seventies with the advent of digital technology. As well as I need to learn more about amplification components in the high end of audio technology. I keep running across terms I don’t understand. I’ll give you a list and if someone would be kind enough to explain these basics I’d be obliged.

For instance I was reading about the Hegel H360 integrated amp that Magico’s Alon Wolf recommended for their A3’s. The review mentioned they were a Class A/B amp, another person commented Class A’s were better, and a third person said he didn’t care for Class D amps. What do these classes signify? 

A second question is about DACs. I generally understand their purpose of the DAC, converting a digital to an analog signal. However my only digital device, the Marantz SA 8005 already has a DAC, ostensibly of good quality. The turntable ’s Ortofon cartridge would not need to play through a DAC, I presume. Would I bypass the CD’s players DAC if I purchase the higher quality Hegel H360 integrated amp?. Or could I find an equivalent integrated amp without an integral DAC?

On the other side of the equation I understand the turntable’s cartridge cannot play through the Hegel without first going through a phono stage. My old Phase Linear 4000 preamp you just plugged the turntables RCA cables into the back of the preamp and you were done. What’s that about? Do they make equivalent integrated amps to the Hegel H360 with integrated phono stages already in place, so I can just plug my turntable in as I’ve been able to do before. The amps don’t seem to be well integrated at all if you have to add a pricey phono stage to make them work, and end up having an extra DAC. That’s just me whining.

Third question is what are monoblocks, how are they used, and what are their advantages to a system? They were used at one of my speaker auditions.

I figured out the answer to what amplifier damping was myself, so I’m sparing you that one, but what does the term impedance mean? I keep coming across that.

Thank goodness I don’t have to figure out the cabling nightmare yet. Thanks for any help.

Mike