Replacing standard speakers in Mk1

[AcID ZeR0]

What are they by looks of them 8cm?
If I put new decent 8cm ones in exactly the same place the old ones are how much diffrence would it make?

Like I don't want 6x9's and stuff because it will only attract attention so I want it standard looking.

I've got twin 15" subs and amp in the boot and the current standard speakers distorts at about 23 volume.

 

[Claire]

on a mk2, the speakers are 5.25 inch. to make any decent difference you need to get them amped, and for that you would need a new headunit.

 

[AcID ZeR0]

Sorry forgot to say I've got a Sony Xplode MP3 headunit and 1000w amp powering the subs at the moment.

 

[Claire]

whats the rms of the amp? and how many channels? just two?
If you do want improved sound - please god do not get more sony speakers!!