VRS Front Speaker Buzzing - replace or upgrade?

It seems as though my front left speaker is struggling with bass frequencies. Its buzzing to most music. I don't know if this is classed as "blown", but it certainly sounds rubbish.

All I want is an inexpensive replacement or upgrade, easily fitted, that would be able to handle bass frequencies far better than standard.

I'll be keeping the standard symphony head unit. No plans to replace it.

Any advice?