Shud be your HU power up the speaker but not the speaker power up the HU!Normally a speaker minimum will need 50rms to drive up it to perform perfectly,but if directly drive with HU power (around 15~22rms) oso enough for normal audience.just if you play in high volume,the output will has distortion and a bit noise lor.
that sounstream comp set shud b the fake product.try mohawk these localise low end speaker shud can meet ur requirement.
if you need more proffessional advise,better goto some acc shop(better goto some reputated shop like KKLAU,KFAUDIO,ACP,SOUNQUEST).tell them ur budget and ask them wat system you shud upgrade.I think they will quote you a satisfy combination choice to meet your expectation.