Sound system in my subaru

i was thinking of putting a subwoofer in my 1995 subaru impreza. right now i have a Panasonic CQ-RX100U as my stereo and was wondering if i could hook up a subwoofer to it and what kind of watts or Hz will work

Check out Crutchfield.com for information about adding a subwoofer. A high-wattage system may strain the battery and charging system in your Impreza. Be careful.

Remember too that subwoofers in general of size > than 8" are useless for a car interior. Anything larger than what’s recommended as an option for the car is likely to benefit those outside more than you. The wave lengths of sounds generated by true subwoofers are much greater than the longest dimension of a cars interior, making these sounds very difficult to generate and typically result in lots of distortion when the effort is made. The typical 100HZ “boom” is all that’s really heard by the easily impressed. Car’s interior is not conducive to audiophile sound, especially in a 95 Subaru. Save your money. Standard quality 6by9’s is more than sufficient with attention given to dispersion using multiple drivers within the capability of the car’s receiver.
A quality sound installation in a modern very quiet car, requires a custom evaluation and installation by a qualified sound tech for lots of $$$$. Even then, it will never approach a cheap home set in a good environment. Cars are the worse there is for quality sound.

I was in front of a new-ish Durango awhile back at night time, and everytime the bass hit, the headlights would flicker something awful.

That’s a self test feature.

According to Crutchfield your unit doesn’t have a sub preamp outputs, but does have preamp outputs, so you’d need a low pass filter and an amplifier (that’s the big $$). Course, anything can be done, just takes $$.