Did you already thing about building a sub for yourself? That would be the cheapest way.

The shape or type of a sub can be very different.
There are following main types:

1 - the closed box
This is - how the name already says - a totally closed box with a single hole filled with a speaker. This type gives the best quality in sound but has not as much power as others have ( less dB than the same speaker in a bassreflex )

2 - the bandbass
This is the most complicated sub-construction. It's a box splitted into 2 chambers. One of these chambers is totally closed and in the splitting wall there's the speaker sitting and pointing to the open chamber. The open chamber has (usually in an angle of 90 degrees) bassreflextube. That's it. This construction is quite powerful but only gives a very small band of frequencies. So you get e.g. only the very deep frequencies and you'll miss some sound between the very low and mid-range frequencies.

3 - the bassreflex
This is similar to the closed box. The only difference is that (holding the same speaker) it's a bit bigger and has one (or more) holes with bassreflex tubes. This construction gives all frequencies quite good and is pretty powerful but in comparision to the closed box it's more noisy and so so clean

4 - the freeair
This is a simple speaker mounted somewhere without any build box around. The box around the free air sub is eg. the trunk itself. It doesn't sound that good and has not too much power.

Of course there are many differences in size and shape of the boxes. They can hold 1 or more speakers, the speakers can have different sizes etc. Generally you can say the bigger the size the better the low frequencies. eg. a 12" sub would play the low frequencies better than a 10" or 8" sub. But this also depends on the quality of the speaker, speaker-chassis, membrane etc.

I dared to build a box by myself. At first I had a bassreflex tube with a 12" speaker. But it was not very powerful so I calculated a new box - this time it was a bandbass box. I used the same 12" speaker in this box. It was a bit more powerful but you could only hear the very low frequencies (as described above) and it didn't sound too dynamic.
So I ended up building a closed box. This is what I have in my car now. It's pretty small and has a very clear and also powerful sound and I'm very happy with it.

Even though the building of a box is a very complicated thing and you have to know a lot about the speakerparameters and calculating the correct volume for your purposes (there are some programs for calculating subwoofers in the internet) it's not THAT important in my opinion. Maybe you wouldn't get the BEST result possible by building a box without calculating it's correct/optimal volume, but it's cheap.
Or you could also get a ready prepared box and you would just have to fit a speaker into it. That's another cheap way to get a good sub.

Good luck - and take enough time - maybe you could try some subs at a car dealer. Then you'll hear the difference and you can decide what would fit best.



TeeMcBee
Got my Mk2! # 080000143