HELLO!
I don't think so, 4" or 5" is not a speaker issue.speakers just
quality optimise and looks powerfull with their no of watts...
I am not sure about these speakers but i know they will be much
better then the cheap set of PC,s speakers...
another way to save money is to change just speakers ,but not
amp..Use the same amp with some 5" speakers...
To make a sound quality in my advise
You should use PC's speakers with more watts...like 300watts etc.
I also set Zoltrix 300 subwoofers in my cab.