From a relative noob...
I bought the PC separately on eBay, then bought a kit like this on eBay because I wanted the extra pads....
eBay Motors: XL Dual Action 6.5 Inch Foam Pad Kit -Porter Cable 7424 (item 300211984277 end time Apr-09-08 13:59:54 PDT)
Then I bought the polishes separately from AutoGeek when they were having a sale and free shipping.
Oh, I had to buy my backing plate separately cause the kit didn't come with one.
In the end, I spent less overall than the AutoGeek kits and ended up with more pads.
For polishes, I started with the XMT line, and they worked well, but I'm trying other products now because it seems you can get as good or better for less money. (Note that the
Menzerna and Optimum kits you listed come with 32oz bottles of polish versus the 12oz bottles in the XMT kit).
Also, I bought all my stuff before I joined Autopia. Now that I'm reading here regularly, I don't see too much mention of the XMT products, but I see people recommending Menzerna and Optimum products all the time.
So, if you're going with one of those 3, I'd say go with either the Menzerna or Optimum since you'll get more product for the money and since those brands seem to be recommended much more often than the XMT stuff.
Hope that helps
