Upgrade question. Rega RP3 or RP6.

Hello,

I am ready to upgrade my set up.
I am debating between a Rega RP3 and RP6 with the stock Rega cartridges. I listen to a variety of music with a large portion of my collection being punk rock. The one thing my current set up is lacking on is bass.

*Will I hear a huge difference in sound quality with one of theses over my current turntable?

*What is your opinion on RP3 with upgrades VS stock RP6?

*Will I notice a huge difference between a stock RP3 & RP6 on my current 2 channel receiver/speaker set up?

*Will a pre-amp sound better over the phono input on my receiver?

*Can anyone recommend a shop in the Los Angles area that demos Rega?

Thank you for any input you can provide on my questions.