Hello,my current pc contains this: cpu i5 3470 2x4gb ddr3 1333mhz ram Asus gtx 960 strix 2gb gpu 500W psu

im the next week or two I want to upgrade some of this parts with the following components: Gpu Gtx 1660(non TI) Msi gaming X 2x8gb 1600mhz RAM and a 240gb ssd sata III also im looking to upgrade the cpu but not right now. My questions are the following: 1. The current Gpu uses a 6 pin power cable and my psu doesnt have an 8 pin cable for the upgrade,is it ok to put a cable adaptor from 6pin to 8pin to power the gpu im looking to buy?from what ive read online the gtx 1660 has a low power requierment so for now i would like to keep the cureent PSU 2. will the gpu im looking to buy bottleneck my current i5 3470 very hard? 3. when i will upgrade my cpu i want to get an i5 3570k or an i7 3770(non K),wich one of these would you guys recommend?

Thank you very much for taking the time to read this and im sorry for any mistakes ive made but english is not my primary language. Edit:im sorry also for the format i dont know how to format for reddit.