Why Can We plug our AMPS directly into wall w/o Worrying?

Baz,
As Garfish intimates, "clean power" is important where the chain is most vulnerable: pre, digital front-end, etc. Power amps are less vulnerable (they usually have very large power supplies of their own), but they DO need to draw current -- hence the advice to plug directly to wall. Given the (often) high current (or voltages), power amps are also supplied with protection circuits that can save them in cases of surges (hopefully!). Finally, many power amps can reach optimum operation level from cold within ~hour; so, less need to leave them on all the time and unattended.
Cheers!

Every component can benefit from cleaner electric power, but digital components seem to benefit the most. It's interesting to note that power conditioners did not become popular until digital components were widely used. I suspect digital components are the major internal causes of electrical noise in home systems.

At one time I used an API Power Wedge and I was never truly certain if it was limiting the sound of the power amps (Rowland Model 1 or Pass Aleph 5). Regardless, I plugged them into the API because I perceived the surge protection as more important than the small, if any, detrimental sonic impact. I currently use a PS600 and I can detect no negative effect on amplifier performance. I am passively bi-amping my speakers and I plug both a JRDG Concentra integrated and a Model 112 power amp into the PS600. With no music the system shows 190 watts on the PS600's display. Loud music (up to low 90dBs) only raises the display to 240-260. I've never tripped the PS600's overload circuit. My speakers are 4 ohm designs with 89dB sensitivity.

Scratch out the without worrying part. I suffered from a near lightning strike this spring that fried some tubes and the B-fuses in each of my amp while everything on the Chang escaped unscathed. When my system was set up differently i had the amps through the chang as well and didn't notice a hugh dynamic shift. Getting a good conditioner/protector for each amp is something on the budgeting list for me since next time it may be more than a hundred dollars worth of tubes.

Try a Vansevers "Unlimiter" conditioner.

I use a PS Audio P1200 with my Krell KSA-300S with such good results that I haven't gone back to straight wall connection. I also use the P1200 in 220V mode which benifits from balanced A/C. I know it is pricey, but if you are like me in finding the components you want then it is a final step and a big sonic improvement.