You can use my DataKick module. It is designed to help with exactly these kind of things. You could:
1) create a custom field on your product (or combinations) named 'Threshold', and then assign different thresholds (in days) for every product/combination. Alternatively, you could create such field on Suppliers, Manufactures, Categories, etc... what makes sense
2) Create list of products with quantities below the threshold
3) Optionally, you can create scheduled task that will daily send you email with exported list of products to order (as csv)
My module has 14 days trial period, feel free to install and try it. Ask questions here if you have any (I'm sure you will have some, as it's a little bit more complicated module that usual)