Historically, there are not many good, simple inventory software that supports "kitting" or combo items.
Even QuickBooks has some important limitations. The quantity available data for QuickBooks "inventory assemblies" must be "pre-built". It is not automatically calculated based on the availability of components.
Teapplix just released support of combo products that allows you to get around this limitation. We solve the quantity available problem if you use QuickBooks. We also gave you this capability if you do not use QuickBooks to track inventory.
Details are from the below link. Ability to define combo items, and track inventory comes as part of our "MultiChannel Inventory" subscription.