Pass Labs or Audio Research Solid State Amplifiers

Audio Research is reknowned for their tube amps (I owned
a D-125 which was excellent), but their solid state amps
have never impressed the masses as much as their tube
offerings. I also owned a Pass Aleph 5 which was an
excellent Class A solid state amp, and occasionally
available for $1500-1800 used. I personally would lean
to a Pass amp as having a more refined sound.

The Pass Aleph series amps are very detailed and direct, but the affordable models are only 30 or 50 wpc. They do have bigger Aleph models and they have the newer X-series, but they start getting more expensive. I would definitely recommmend listening to some amps in your home before buying. I'm not sure if you would like the sound of the Pass with Megadeath or Metallica. I'm not putting down the music at all...it's just that the amps are very detailed and neutral, and you may not prefer the way their lower powered amps portray distorted rock, and they may not be able to go as loud as you might prefer. I owned an Aleph 3 and, though I appreciated a lot about it's design, purity, and musical detail, I never found myself tapping along as I listened. I constantly found myself distracted and I wasn't enjoying the music. It's an amazing amp, but it wasn't the right amp for me...with my system.

All amps are designed by people with individual tastes and they will appeal people's individual tastes. Some are better at portraying certain styles of music than others...probably due to the designer's individual tastes. Besides all that, you need to know how the amp will mate with your preamp, speakers, and the rest of your system. There are many amazing preamps, amps, and speakers, but they won't sound amazing if they're not matched with compatible components...that's why it's so important to try the amp in your room, with your system and your music.

i think people here will want to know about your associated gear, especially the speakers you are using or speakers you plan to use. the speaker/amp combo should be well thought out for synergy. if you are using a budget speaker, you will likely upgrade that after your amp purchase, and some, including myself, do not think you should proceed this way.
i would pick the speaker i wanted to voice and then choose from an appropriate selection of amps. consider, if you have a fairly to highly efficient speaker (>= 90db sensitivity with a fairly flat impedance curve) you will likely not need a monster ss amp and may find yourself very satisfied with a pass aleph series.
the bottom line is that many feel the amp should be chosen for the speaker it is intended to drive and rarely the other way around.
let us know more about your system

For metallica and 'megadeath' I would definitely stay AWAY from pass labs aleph amps. They have very precise bass, but in your price range the aleph 3 and aleph 5 will be too wimpy. I too have heard that the early ARC solid state amps stank. I have not heard one personally to confirm this. Seems odd that they would have let it out the door.

I would buy an old conrad-johnson mv-50, 52 or 55. These are el-34 based and make electric guitars sound GREAT. No other amp brings out the real sound of an overdriven electric guitar so well. You should be able to find one of these for 600-1500 depending on year/model.

If you want bass string for 1200, buy a mccormack dna-1. Those have awesome bass. If you can find a dna-1/reva or revb you might want to pay the extra cash. Also, the adcom 5802 is a great 300w amp. You can pick those up for under 1000. They are very good sounding amps.