Hello Andreas,
Adagio OrderEntry supports 6 different order import layouts. If you could tell us the layout of the record being genereated by E-transact, we could tell you whether Adagio OrderEntry is capable of importing it directly. Contact me via e-mail if you'd like us to make sure the process would work correctly. We'd need to test with a copy of your data and a sample import file.
There are 2 Purchase Order options available afor Adagio. If you are using Inventory Receipts (which is from UniDevCo incidently), then you'd want to look at Purple IR for Adagio, which will work with your existing IR data. They have several successful installs in North America. PO Tracker implements the purchase order processing available in ACCPAC Plus Inventory control.