2001 tahoe stereo

I have a 01 tahoe with a factory amp running the speakers. I have replace the head unit with  pioneer 6500dvd and I'm wondering if replacing the front and maybe rear with kicker k series 6 1/2 or polk db will make a difference? The stock speakersth are 4 ohms.

Also what would you guys recommend for  amp, i'm thinking of running two kicker l7 or one 15. Which configuration do you guys like better. Is there any difference between last year models and this year. Is the only difference between the L7 and L5 is the power that it can take ? I'm setting my budget between 500 to 700. I'm thinking of getting my stuff on fleebay or online.  Any help would be appreciated. Thanks

  I'm not quite sure about all the technical number junk, but in addition to handling more watts, I think the L7's have a longer excursion.  Longer excursion = more displacement (air movement) = more bass.

    As far as your budget - BEWARE.  I recently got 2 12" L7's and let me tell you, they definitley are an investment.  Be prepared to go big in order to get their full potential out of them.  You'll need a huge amp, huge wiring kit, upgraded alternator, lots of dampening product, two boxes, etc.  I've spent $2,000 already and I still need to buy some nickle-and-dime sh*t.  I'll tell you though, they're worth every single penny.