Conditional auto-filtering to summarize data

[trigger]

I want to make a worksheet that will summarize the data from two
spreadsheets, called "cars" and "parts", which have three columns each,
one for description, one for SKU, and one for quantity.

I'm trying to make a third worksheet display only those rows in the
other two worksheets with a quantity of greater than 0. I want to split
the third summary worksheet into two horizontally split sections, one
for cars, one for parts. I need to subtotal the "parts" and subtotal
the "cars" sections, and then make a grand total.
so the third worksheet would show

Code:
--------------------

SKU Description Quantity
A5486 Mini 5
A8788 Bug 1
A5544 Lexus 8
Car Total 14
A8888 Muffler 1
A5433 Transmission 4
A6633 Brake Pads 3
Part Total 8
Grand Total 22

--------------------

I want this to be a dynamic worksheet, so if you change the quantity of
a line item in "cars" or "parts", it will automatically show up in the
third summary worksheet.

Can someone help me out a bit? I'm lost as to where to go on this....

 

[Max]

Here's a sample file which provided some ideas:
http://www.savefile.com/files/6395325
AutoExtract n Stack Qty Lines From 2 Sheets

Sheets: 1 & 2 (Side-by-side output)
Sheets: 1a & 2a (Stacked up output)