Accuphase or Leben for heavy metal

Neither.

Parasound Halo A21+

300 W x 2 @ 8 ohms

500 W x 2 @ 4 ohms

I also listen to heavy metal and what I found that sounds good is AB 250W amp that is capable of pushing about 40W class A and speakers that are no les than 94db, also big deal is a preamp, less complicated is better. My first system that was producing really great HM was Threshold S550e paired with Threshold FAT10 or Threshold T2 pre and JBL 4367, they  do great job with neutral sound and very dynamic sound, I upgraded from that system  to Pass Labs X250.8 and Pass Labs XP12 pre..... now that's impressive sound !

+1 @lalitk on SPL

Their stuff is powerful, dynamic, clean, holographic while balanced, yet still super nuanced. I’ve got the Elector pre and have to say that I’m enjoying everything from chamber jazz to AC/DC with two different amps used so far. Something about that high voltage rail tech they’ve designed.

Elector pre + Performer s1200 or Elector + s800 (budget option). They also have incredible mono amps. But looks like you want to stay with an integrated and hope I’m not colluding the discussion!

I do need to add, however, that those Piegas are sensitive enough to not need too heavy a wattage amp. You may not need so much wattage to drive them to concert levels, and that current via power supply and capacitance delivery (both in speed and sustained demands) by design is way more important than overall wattage. But wattage does help. My uneducated guess, at least 120 watts per channel would be fine if the amp is down to 2 ohm stable.

Also, are the Piegas floor-standers? And what’s your room size?

@OP  Passlabs X250.8 with an appropriate pre-will work very well on metal. As reflected in many of the comments, you need the ability to play loud with lots of control.

A pair of Parasound JC1s would also be ideal - preferably pre owned. Since they moved to the JC1+ they have gotten very expensive.

Both the Pass and Parasound are biased in to Class A for the first 25 watts so they are pretty refined on acoustic music too.

Metal music is actually one of the least demanding musical genres for amps and speakers. It is heavily compressed during recording and mixing and then heavily limited during mastering. Most metal has very little dynamic range which makes it easier to reproduce than jazz or classical.

Assuming that your speakers have a reasonably benign impedance curve you can get away with fewer watts for metal than you would need for other musical styles. However, I think that with 90 dB speakers both of the amps you mentioned are under powered. I would consider something closer to 100 watts so that the amp will be running in its sweet spot when you listen loud.