for a good sounding set up i wouldnt go for 6x9"s.for a system that sounds a bit louder then 6x9"s should do the job.using a stealth shelve may improve the 6x9"s but for a cheaper option try a bit of mdf underneath the parcel shelve this should give similar rusults and be alot cheaper.the only advantage of the stealth shelve is no theiving scumbags can see your speakers.
if its a sound quality setup id start with changing the h/u get decent components and sound deaden the doors and fade out the rear speakers.
its only a small car so a good set of speakers in the front will fill the car easily.sound deadening the doors will
help reduce the panel vibrating and
help get the best sound from your speakers.
to get the most from aftermarket components its always best to power them with an amp.running an amp does not just mean your tunes will be louder.the amp produces a much clearer signal from your h/u and delivers it to your speakers giving a much improved sound.theres not many h/u"s that wouldnt benefit from using an amp no matter what make or cost the h/u is.
teaming up a decent set of components with a sub-woofer is by far the best way to get a good sound in my opinion. the best sounding setups ive heard only have components in the front and a sub in the back.a sub however does need an amp to power it. also if you do decide to get a sub different sizes are suited to different music styles so dont just go for the biggest one you can afford.
if you are buying an amp head unit or speakers always remember that the power figure on the box is alot of the time a lie to fool people who dont know any better.they put figures like max power 700watt or 4x80watt ect when the actual power can be found out by looking at the size of the fuse and multiplying it by the 12volt power from the battery that it will be running off.
so if your amp says something like 500watt and has a 25amp fuse in it multiply 25amp by 12volt and you get a better idea of your amps real power.