Integrateds: Why do they all SUCK?

Looks like the only thing that "SUCKS" is the OP's dumb question.

Integrated amplifier vs. separates?  It all depends on who's baking the bread. Certainly if you tell your design team they can design without sharing the apartment the end results have the potential to outperform.  This assumes we are operating at the same level of engineering, have access to the same technology, and with almost unlimited parts availability. Some IAs will dramatically outperform some separates while also costing more. Like most things it ultimately gets down to money.  Not just the cost of the component. (Some very expensive devices still render poor sound quality). Access to quality R&D (money) is a big deal.  Despite the subjective nature of the exercise this same thing can be said of loudspeakers.  Regardless of your budget consideration should be given to the manufacturers operating budget, access to technology, the quality of the design team, and the overall commitment to excellence.      

Sugden A21 SE is a very good piece, pure Class A

I went down this path for a long time.  

I started out with a Micromega Minium Amp, which actually sounded great.  Excellent phono stage, very high-resolution sound, very dynamic, even a great headphone jack.  After less than a year, it started blowing devices in the power amp section.  They were hard to come by, and there was no service center for Micromega in the US.

Then I went vintage for a while.  I used an Advent Model 300 for several years.  Not bad, but it doesn't really get your toes tapping either.

Looking for something better lead me down researching the Rega/NAD/Arcam amps.  I was ready to pull the trigger on an Arcam, when a dealer convinced me to listen to a Naim Nait 5i.  I was done for.  

The Naits are all fabulous integrated amps, regardless of the particular model.  Unfortunately, newer models don't have integrated phono sections, but I prefer the modularity for easy upgrades.  They are all Class A/B as far as I'm aware, and most have active preamps.  Many have the ability to upgrade to a higher-quality outboard power supply.  The DIN connectors really do sound better than the RCA connectors, even if you're using an adapter cable.  One caveat is that the original Nait 5i (non-italic) has a passive preamp section, and the Nait 5 has a volume control that a lot of people didn't like.  So you might want to go older or newer than those two models, which were current around 2003-2005.

Regardless, that one piece of gear made me a true believer in the Naim sound.  I now have separates, a Naim CD player, and a couple of power supply upgrades.  Their equipment tends to hold value well, so upgrading is fairly easy.

I refuse to continue to respond to this thread and I encourage readers to pretend this refusal doesn't exist as responding by noting you're not responding is responding, and therefore a paradox.