Customisable computer system(s)

[tin2001]

We build custom PCs at work. Currently we use paper "menus" with the base system at the top and a categorised list of optional addons/upgrades. Practically all the options are exactly the same on the different model sheets (for the purposes of this, we'll assume they are the same), with only the base system varying.

I have already worked out that I could create the base systems as products, then use cart variant custom fields for the addons, but this would get messy and painful to keep up to date.
Is there a way to have a list of addon options that I can apply to all the base systems so we can edit them in one place?
Please assume I'm a n00b when answering that question - and tell me if I'm being stupid :p

I know there are addons like the kit builder one, but I would prefer to avoid addons if I can.

Edit: I should mention we will NOT need to track stock - at this stage we will be using this internally for in-store sales only, not internet sales.

[balai]

http://breakdesigns.net/extensions/vm-product-builder

[tin2001]

I know there are addons like the kit builder one, but I would prefer to avoid addons if I can.

I already knew about that addon. As far as I can tell, we don't need anything that complex - we don't customise anything that requires more than dropdown boxes to pick addons.