1) AVR measure as well as class A analog stereo preamp in terms of FR, THD, XTalk, SNR. In fact, some AVR from Denon, Onkyo, Yamaha, and Pioneer have measured better than some analog preamp. In addition many of these AVR give you a lot more features like bass management/subwoofer management, channel gain control, etc. They also look better aesthetically to my eyes, and aesthetics is huge on my list.
BTW, I used to own four Acurus RL11 Class-A Analog preamplifiers. I used to be almost 100% analog. They measured exceptionally well and sound awesome. But I found that they don't sound any better than even a $400 AVR in Direct Mode.
2) The Audio Critic was the 1st publication that made complete sense to me. For example, I could never tell the difference between my amps when level matched. I could not even tell the difference between preamp + amp vs AVR in direct mode. I could not tell any difference between my Kimber Kable, Audioquest, Vampire Wire vs Radio Shack wires. I thought I was crazy. But The Audio Critic dispelled all these things. Double-blinded studies have proven that amps, preamps, wires, DAC, & media players just pretty much sounded .......well, the same or at least so similar that most people couldn't tell the difference. Most people. So I think it is possible that some people can tell the difference. I'm just not one of those people.
3) Theoretically you would still have some benefits of the Pure-Balanced fully balanced tech even if you use RCA unbalanced cables. Just like theoretically you would still have some benefits to passive bi-amping.
The AT2000/3000 also have the "fuse-less" automatic reset circuit feature. My understanding is that you don't have to worry about blowing any fuses on the amp. When I had my Acurus 200X3 amps, I had to replace some fuses. I don't think the AT1800 has this feature.