Sub units for cars

Hi there, wondering is any one here would know what a good sub would be for my brother. Would be his first one so looking for something good, reliable, basic and cheaper. Its for a four door car. No idea where to have it mounted/put, what brand is best or where to have it done.
If any one knows of any Dunedin businesses that they could recommended would be great.
Thanks

Four door car, put it in the boot, bass doesn't need to be directional so can easily fit in there without affecting quality. DO NOT put it in the parcel tray (lord knows why people do this.). Get a decent box for it, buy some metal "L" hinges from Mitre 10 and screw the box into the wood covering the spare wheel mount (this doesn't damage the carpet, and has always held mine in place for years. Velcro on the bottom of the box is just a waste of time, but this can be in addition to the "L" hinges and will keep it VERY stable).

Spending a bit more money will be worth it in the end. I've had a sony Xplod amp and sub for 3 years now, no hassles and works very well.Get an amp that can handle or works above the RMS rating of the sub (ignore peak wattage, it's rubbish). So a D-class amp with an RMS of 1x400 will easily power a sub with an RMS of 300W, just make sure not to turn the amp up too high. If you buy an the amp that has a lower RMS rating than the sub it will constantly shut down from overheating if you drive it hard. Hope this makes sense and helps you, good luck.

I got my brother one of those 10" fusion tubes with built in amp for his hatchback from supercheap. Sounds good, goes very well/loud and was cheap at around $250ish I think on special. He loves it.

As above in the boot. I have used industrial velcro on mine to secure it to carpet. It hasnt moved once, nice and easy no holes and easy to get spare out.