hmm i can help u to have a nice sound system for u,

do ur handphone have mp3?? if yes get a audio jack for ur phone and get a audio to RCA cable both male,
bot of it cost under RM 40
then get ur self a pre-amp brand calibre 5 channel enough edi under RM90

then find a capalang amp enough edi,brother got sell RM100 below get 800watt amp,i got mine SAGA brand 4 channel can say not bad lar,bass not bad
only use 2 channel to kick 4 5'' mid bass and 4 tweeter
when play techno song still got abit kick

use the rest of the money to find any speaker u can find with that budget
RM250 still can get good 2/3 way speeker from brother lar.

if u know how to install the speeker and stuff ur self u save abit lar
i buy and install my self hobby mar lol

ya for got u need to buy extra 2 more RCA cable for ur HU and ur amp
so another 50 bucks, so budget for speeker RM200

so installation part,
HU connect to pre-amp, audio jack connect to pre-amp,
then at pre-amp output connect to amp. so the speeker no need to teach edi lor.
with the pre-amp u can switch channel so u can use the HU or mp3 player/handphone

For my myvi...I only installed an amp n sub....along with a new bracket (carbon fiber) and a new HU. As for speakers...the stock ones are doin fine for me. If ur one that needs clarity n like to turn on the volume...then u will need to change the speakers.

personally i think an component set will give better clarity than a hu, due to the extra tweeters and passive crossover. just my humble opinion, dont shoot me if im wrong.

based on my experience on my Vi
take one 10 or 12 inch woofer plus a set of tweeter will do
but its depend on your budget to get better or worse quality product

If possible get amp for ur Myvi