Should Amps be plugged into a power conditioner?

Depends upon the amp and the conditioner.  Conditioners that allow many amplifiers to function without limiting the headroom are very expensive.

This ^^^^^.

Some amps (mainly higher end amps) go to great lengths to optimize the power supplies in the amps.  Others can definitely benefit from a good conditioner.  It's just not a one size fits all rule of thumb.

I got a chance to buy a used Lightspeed 3200 for $10, so I gave it a try.  Wow....really nice with my old tube amps, but can't say what it'd do with other amps.  YMMV

In general no unless perhaps if one has a power conditioning device capable of delivering the power and current the amp demands without breaking a sweat. Pencil neck conditioners need not apply with most power amps. Otherwise the power conditioner will be a bottleneck to performance rather than a help.

Thanks to all for your feedback. I should have mentioned what my model my amp

is. It is a AR 300.2. Kind of old, but still a very good amp

. 

Prior to purchasing the Shunyata Everest 8000 and a bank account’s worth of power cords, I spoke with various people and researched the topic of plugging power amps into the wall.  My integrated amplifier, the MA12000 at 300 watts per channel of not class D power had a definite McIntosh recommendation of plugging it directly into the wall.  My MA12000 and two REL S812 subwoofers each plug into their independent circuit on my Everest and I’ve never found anything but benefit from using the Shunyata.  Take a look at this review with reference material and components used at the end of the review.  I’m not suggesting that you do the same.  In fact, as previously mentioned, I purchased these with a ninety day guarantee of 100% refund if returned.  I fully expected to return the Shunyata and their Midas power cables.  I didn’t…

I've been very happy with my 200 watt amp from Spectral plugged into an Equitech 2Q which is a "balanced power" unit.  I use very high level MIT Cables power cords to and from the Equitech and found a benefit with these MIT pc's. I would not be without the 2Q. My cities power is not excellent; as many others are not either. YMMV. I decided to buy the 2Q by an in-home trial. It was a no brainer on listening; but not cheap.