Help with power supply board!

Hello i have a dell t5810 with a 685w psu and currently running a GTX 1080 I spent the money during Christmas to buy EVA 1080 TI 11 GBSC But this card requires more power and an upgrade from my original eight pin. This one needs a eight pin and a six pin power supply board only has one dedicated GPUVGA I read another post somewhere on here saying you can use the empty CPU two Slot so I bought a 10 pin connector To a 6+2 connector and I try to use that to be my second rail for my GPU but every single time I plug in the CPU to wire power the whole system won’t turn on! I messed up and I already pulled the trigger and bought a 825w Dell PSU hoping that it will be interchangeable but I realized I still will only have one dedicated GPUVGA available and I won’t be able to pull anymore power even though I have a bigger power supply or can anybody give me tips to Why I can’t use the CPU to power or if there is anywhere or another part for the power supply board with two GPU Slots so I can pull the necessary 250 W that I need? Please get back to me with any ideas. I’m about to just can it and sell the 1080 TI because I feel like the fans were too loud when I did get it to run and try to upgrade to rt  3070 Which also needs 220 W so I’m also scared to waste more money. I’m already $400 in the hole with all the adapters and the new power supply and graphics already bought.!! HELPP PLZ THANKS AND GOD BLESS for your time!!!