If you decide to self-source, then order as many things as possible from a single shop to cut down on shipping costs. The benefit is you can customize everything to your liking and have spare parts for the next Voron you build. 1700 euros seems high to me, but I haven’t built a new Voron recently. Try checking the Discord to see if there are any cheaper places to get kits.
As far as suppliers, I’ve heard good things about Fermio for self-sourcing components. Most of my parts came from Aliexpress. The Voron website has a great self-sourcing guide you can use that includes links. Nero3D (Canuck Creator) has some older livestreams where he walks through the sourcing guide and talks about the different things to look for on Aliexpress.
The trident is a fantastic printer and you will spend a lot of time and money on it no matter which route you choose. Now is probably the best time to plan out which mods you want as well.