Dumb question......why do you need a preamp?

I think it is pretty obvious why an integrated amp, in most cases, is not going to sound as good as separates. I know of several people that drive their tube integrated amps with a separate tube preamp. In my experience the preamp section rarely matches the quality of the amp section or vice versa. The only reasons to go with an integrated would be size, cost or simplicity. 

Some say a separate preamp offers more choices. Some say it introduces more possibility of unwanted noise because of the extra component and cables to connect them. Some say it's mostly a way for dealers to make more money. I fall into the latter two camps. 

Then there's the mostly erroneous belief in "synergy." If you believe in that, an integrated amp reduces that possibility. 

if you have an integrated amp, you don’t “need“ a preamp, but most people would likely say that separates of comparable make or quality to the integrated app will be better.

Some say omitting the preamp and running the dac directly to your power amp is superior and a lot of others who say just the opposite. I’ve tried both in my system and definitely prefer the preamp, I think it adds a density and richness to the sound that is missing otherwise. There are, however, plenty of knowledgeable people who disagree. Like so many matters in this hobby, it’s  a matter of personal preference, not a hard and fast rule

I make the world best sound audio system with an integrated amp. My audio system will sound worse if I used a separate pre-amp and power-amp configuration system. Also, my system will sound worse if I used separate transport and DAC. Alex/Wavetouch audio

A good separate preamp will 95% ofthe time sound muchbetter 

most integrated amps have cheap little roundAlps volume attenuators which are not good and Rob detail ,you want a zr2R resistor ladder attenuator, then relay 

for top quality.