Does anyone know how powerful this OEM amp is?  Behind the passenger (left) seat side panel.
"How many what's ?"  - I hear you ask. 
"Yes that's right".
Do I recap it (cheap) or replace with a new one with probably more power. $$$
 
 

In the 90s I worked in car audio etc, current quality aftermarket car radio would have more watts than the Toyota amplifier, more importantly the amplifier technology has come a long way (sound quality).
Recap or buy a modern amp, depends on the cash in your pocket and what you need it to drive.
Personally, throw the Toyota one in the bin and get a good head unit or add an external amplifier.

Thanks Tony, perfect response. I will bin it. I have a nice Alpine head unit, (only 25W) and some Alpine speakers.
Sounds pretty good, because the Alpine has lots of features / adjustability, but lacks proper current drive to provide bass/low mids effortlessly.