if i was to pick on a budget of £200 i would go for
this is an active sub with wiring kit, i fitted 1 of these to a mates car and was very suprised with how good it was for the money
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A head unit like this ( just using this as an example your choice entirely )
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and then you should be left with enough to get some cheap components like
these or
these
thats a total of £179.96 with the ground zero comps or £190.97 with the vibe edge comps
remember quality is compromised when shopping really cheap, the vibe edge stuff tends to be a good starting basis from what ive gathered