Of course you can turn the volume down.
200 WPC is relevant for people who use an AVR such as the X3500H that does not have the ability to disconnect any internal amp channels. So based on ASR measurements, the AVR-X3500H pre out would go crazy (Amir's high bar only, high=higher than other reviewer's such as AH, HTHF, S&V just to name a few..).
Now take a look of some facts below:
- many external power amps have gain around 29 dB, some goes as high as 32 dB, but the likes of Outlaw, Anthem, Monolith, ATI, NAD, Emo have gains between 28 and 29 dB.
- the AVR-X3500H, as measured by ASR, has SINAD in the mid 90's, that is about 0.0017% THD+N at 1.2 V and based on Amir's comment, it is reasonable to assume at 1.4 V, before it starts to go crazy pass 1.5 V, SINAD would remain in the 90's.
- At 1.4 V, a power amp with gain = 29 dB will be driven to almost 200 W.
Some based on the above listed facts, if one pairs the AVR-X3500H the likes of the Monolith 200 W amp, one would be able to drive such amp very close to its rated output with SINAD not lower than 90 dB, that is 0.003%, not SOTA, but as good or better than its much higher end cousin the AV7705 that is a dedicated preamp/processor.
No problem to pair it with a 400 W amp either, just that one would have to expect at volume 0, SINAD will drop to about 73 dB, that is about 0.02%.
Again, you are right, just turn the volume down if one can hear THD+N as low as 0.1% (I doubt it would be higher than that even at volume 0) at the power amp output.