At the bottom of the armrest storage area, there are 2 or 4 10 mm bolts. It breaks free and leaves the front part of the console, around the shifter, in place. If you need to loosen the front console, pull out the shifter surround, there are bolts in there IIRC.
The hardest part is finding an amp just like yours. The part number on it will read something like "12345-A018C." You will need to find one with the exact same part number as yours.
Although I cannot find the NUMEROUS old threads that existed on this site describing the "low volume rear speakers" problem, it seems pretty well settled that the earliest years Sequoia had a problem with that JBL Amp.
In fact, Toyota TSB AU00102 in February 2002 specifically addressed this amplifier problem.
Accessing the Center Console to remove/replace the JBL amplifier powering the rear speakers.
The bolts you'll have to remove have 10mm heads. Locate a crescent wrench, a long extension if you have one, and a 10mm socket. A flat blade screwdriver may be helpful in removing the wiring harness plugs, I just used my finger nails.
1. Remove the shifter knob on the center console 4WD shifter (assuming you have a 4WD model).
2. Grab the center rib of the console tray (the tray under the shifter) and lift straight up. The black tray with leather shifter boot popped up and out quickly easily without prying.
3. Next you'll need to remove four (4) 10mm black bolts to lift up the center console to get to the amplifier installed underneath.
4. Remove two bolts at the rear of the opening under the tray just removed, at the front of the center console.
5. Open the center storage and pop out the plastic CD organizer tray from the bottom of the center console storage area.
6. Remove two 10mm bolts in the bottom/rear of the section.
7. With these four bolts removed, grab the front of the center conole section and lift up and back, the center console will pop apart from the front console skirt.
8. To improve access and tilt the console back higher, remove the wire bundle clip right under front of the console (probably AC controls).
9. The JBL amplifier is held down by two gold colored 10mm bolts, remove those.
10. There are two wire bundle connected to the amplifier, squeeze the tabs on the white wire bundle connectors to remove them.
11. Remove the JBL amplifier.
12. Reverse these steps to bolt everything back up.