You really should know this but you need AT LEAST .28s to get any kind of range and accuracy out of your gun. Especially with a nineball bucking. I would send back the .25s and get a bag of KSC .30s . Also, the DBC 6.01 plenty tight enough and an excellent barrel, plus its in the US and cheaper than the EDGI.
So pretty much you should
1. Get some .30s
2. Save for DBC tight bore, and use the rifle with tightbore and bucking for awhile and enjoy it
3. Save up and get pisont/trigger upgrades
Also, I wouldnt get the teflon cylinder because the teflon wears off and I havnt heard any good things about it except, only temporary improvements . I think if you do the DIY mods, Nineball bucking and DBC tightbore you will be very satisfied. I gaurantee you will be happy with the performance compared to your m14. And about the screws, Ive had mine for awhile and my screws are just starting to show some wear. You just need to be careful and not man handle it too much.