go ahead.. it shouldn't be a problem. make sure you use switched power on the amp, or you will kill the 12v. anything over 800watts is excessive in a prius.. the cab design resonates well.
Only if you want to destroy your hearing. (This from a 31 year old with a distinctive loss of midrange hearing due to 12" subs as a teenager.)
I have a 10" JL Audio sub in mine, with a 400 watt JL amp. Speakers also changed, professional installation. Plenty of bass unless you are a hip-hopper who wants to trigger earthquakes. The system will drain the 12 v battery dead in about 30 minutes if the car is on IG-ON. Longer than that, I have to leave the car powered on so that the engine charges the system.
I fully agree. When I replaced my door speakers with Infinity 2-ways they were actually more efficient than the stock speakers (more listening volume for less input from the receiver). I then added a Clarion 5-chanel 500 watt amp and a 10" Rockford Fosgate Punch subwoofer (both realtively efficient). I have no trouble with the 12v battery, but I don't sit and listen in "ACC." The amp automatically switches on and off based on signal input from the receiver (adding yet more relay clicks and clunks from the back of the car when cycling the car on or off!).
I had a 12 inch sub in my car the other day, I had 2 problems with the whole deal. I couldn't eat it all, a 6 inch sub would have done the job and; Some of the filling spilt out and the sauce made a mark on the upholstery. Damn subway!! I'd go a 6 inch sub and maybe a cookie and a drink, 12 inch subs are just a little big.