Proper Treatment of Inventory Items

I'm trying to figure out how to maintain correct inventory reporting when items which are identical except for variations like color, size, etc are sold separately and in build to order configurations. I will use some apparel examples for clarity although my specific items are not actually apparel. Here is what I have.

• Assume I market three colors of the same gym socks, red, white blue. I want to sell these individually from one store page (there is no other variable like size). To maintain inventory by individual colors I assume I must use the Apparel add-on.
  
• Assume I market three colors of the same shirt, red, white, blue. I want to sell these individually from one store page (there is no other variables like size). To maintain inventory by individual colors I assume I must use the Apparel add-on.
• Assume I market one pair of jeans - no variables like size or color. This can be marketed using the basic ProductCart webstore page and proper inventory will be maintained.
• I want to offer the socks and shirts as a combined offer, i.e. 9 different combinations. BTO does not seem to understand that there are three different socks or three different shirts.
• I also want to offer the socks and shirts with the jeans. Same BTO issues.

          How does one set up these items so that ProductCart keeps track of inventory properly in all the situations above?