Purchase Woes

I've pretty much decided which speakers and amplifier I want to buy for my 2003 Mitsubishi Eclipse GTS Spyder with the Infinity system. I plan on buying the following:

• Rockford Fosgate Power T400-4 400 watt multi channel amplifier
• Rockford Fosgate Power T1693 6x9" Full Range 3-way Coaxial Speakers
• Rockford Fosgate Power T1652-S 6.5" Power T1 Component Speakers

I am keeping the original Infinity head unit for now, though. The issue that I'm having is I don't know what else to buy for installation. The speakers come with mounting brackets and the amp comes with mounting hardware. Also, my car came with a dainty little amp under the passenger seat, I don't know if I can use any of the original wiring they set up for that amp. Here are my questions:

• What type of amplifier installation kit would I have to buy for this amp?
• Do I need to buy any supplementary installation tools for the speakers?
• Will my factory Infinity head unit connect directly to the amplifier or will I need to buy a separate kit for that, as well?
• Will I have to completely rewire the speakers to my new amp?

Thanks in advance for any information you can give me!