DV Info Net - Best Mac for HDV Editing

I am about to buy my first Mac in almost 15 years. I want to move to HDV editing and FCP 5.0. I plan to start doing freelance HDV work. Here is what I am considering.

Used G5 with dual 2.7 ghz processors
Video card with 256 MB
4 gigs of RAM
Hard Drive: I will add as needed. I plan to buy 500 gig drive and install it

That's about it. I have continually seen these used system for sale for $2k, with a year of applecare left.

Is this system going to cut it for raw HDV editing? My funds are limited (needless to say).
Or...
Do I need to go with a G5 Mac Quad?
I'm not even sure what the main difference is (I am new to Macs).
How much can I expect to pay for the quad system?
Is it worth it?
Finally, I understand that FCP wont run on some newer Mac Intel Processors? That I got from Apple, but didn't understand what they were saying at the time because I knew even less then than I do now.

I tried to find a thread that answered these questions, but couldn't (found one close to it on the MacPro processors and RAM choices).

Really need some guidance before I start spending thousands.

Thanks.