Well The sound system I have used produces reasonable sound, keeping the costs low. Here is its discription. So I know the whole world out there may have better systems, But when I used to own the daewoo I went for economy in every thing. Untill i recived my oriel prosmatec
Front speakers: keep them original daewoo
rear speakers. Poineer diatone, i.e chinise make they give a good bass, and only for 1700 rs.
Woofer: PROAUDIO. 12". If u do not want to spoil ur back speaker board for the woofer then go for a case in the boot of the car. There are smalles cases and some larger one giving more reverbating space to the air. Buy the larger one. But connect them using plug so that u can take them out some times when u want to reclaim luggage space.
AMP: any good 400 wat amp will suffice for making daewoo thunder.
However: With the above setup u need a good HU. I had and also recommend any poineer unit with follwoing features
FIE: front impact enhancer, really make those front lil original daewoo speakers sound good, by using them for low and mid, rear for mid and woofer for u know BASS
Seprate mid control, in adition to bass and treble control. And a sperate bass woofer control for incrseaing intensity. I.e u can have ur four speaking giving really pitchy notes , high on treble,. But can turn the indivual bass of woofer sky high for some movers and shakers.
But just attach the woofer with the amp, leav the speaker connected to the HU.
I used poineer carrozeria Cassete HU with flip and detachable front plate. Attached a 12 disc changer with 9" lcd screen mounted on the dasboard. Whole system costed my just 24 k rs and gave better sound then many expensive systems