Separates vs. Integrated

One reason to go with separates is to be able to use a tube pre amp with a solid state power amp which is popular with some people. I think BAT has a new integrated that has a tube pre with solid state power amp sections but otherwise you need the separates if you want to do this.

This is a good raised question since I was also analyzing +s and -s for separates v.s. integrated. Designing an integrated amp there is only a minimalistic need for the preamp section that must not even have a positive gain or even have it passive. No need for extra- pair of interconnects.
Tube pre- and solid state amp integrated designes are plenty as well so I don't think that the statement of Philjolet is the reason.
Just by banal view have anyone of you seen a high quality integrated 300W/ch/8Ohms? I didn't...
In case with SS design for both parts there will be a huge deal of space needed for heat dissipation along with heat influence on elements of both amp and preamp section. Power supply issues are also bring a conflict between two parts in one amplifier.
In case with tube-pre and SS amp in one integrated there will be no heat influence on tubes since tubes are not affected by the temperature changes but they're even more affected by the power supply conflicts.
Nowdays, there are quite a-bit integrated amps that realy do make sence but if you have sufficient enough power for your speakers.

Separates usually have better power supplies, and can isolate the preamp/amp power supplies from one another.

BTW, here are some positives FOR the integrated, taken from stereophile:

Why is the integrated more economical? It's less expensive to build, having just one chassis and shipping carton compared with (multiple). Each chassis and its carton add greatly to the cost. Current integrated designs get rid of internal phono stages and achieve further savings with a closed design that doesn't interface with other amplifiers or preamplifiers. This eliminates the circuits for a preamplifier output buffer and power-amp input buffer.

There are other savings. Packing a stereo preamplifier and two amplifier channels into one chassis saves space. Hum is reduced because amplifier and preamplifier now share exactly the same ground voltage, so less shielding is required. And an integrated weighs less—when did you last own a basic amplifier that fit on a shelf, or, for that matter, could even be lifted by one person? No more tripping over massive, sharp-finned amplifiers in the dark. Equipment clutter goes down, and the spouse acceptance factor goes up. This "sweet spot" of compact size and affordability keeps the integrated alive.

It's the power handling stupid (in my best Bill Clinton voice!). I agree with Marakanetz above, I've never seen a 300W/ch integrated amp. Most integrated don't seems to be aimed at those who need lotsa power.

For me, I initially switched from a receiver (aka intergrated with tuner) to separates just so I could get more power (150w into 8, 250 into 4), which my speakers sorely needed.

Nowadays I like having my tube monoblocks, which let me run short speaker wires, and long interconnects. I can now place my audio rack in a bass minima - away from my speakers. Sort of nice.