An RTX 2060 tends to be around 20-25% faster than a 1660 SUPER. It also features some hardware for raytraced lighting effects in the handful of games that support them so far, though it's questionable whether that hardware is fast enough to run those effects adequately at 1080p resolution, as enabling them will still cause a rather large hit to performance.
If you can find a 2060 for around $300, then that's around 30% more than the price of the lowest-cost 1660 SUPER for around $230. So, technically, the 1660 SUPER would be offering slightly better performance-per-dollar than a 2060, however, it's close enough that either would be relatively close in value, and it may still be worth paying the extra 30% if you want that 20-25% more performance and a couple extra hardware features.
However, looking at current online prices in the US, only one model of 2060 with a single-fan cooler is currently available for $300 right now, while other models are $320 and up, which makes the price difference 40% or more for one of those 2060s over a 1660 SUPER, which seems a bit more questionable.
2060:
https://pcpartpicker.com/products/video-card/#sort=price&c=436
1660 SUPER:
https://pcpartpicker.com/products/video-card/#sort=price&c=450
Personally, I would prefer a 2060-class card, but it might be worth waiting a bit to see if prices level out. As for the 1660 Ti, it tends to not be more than 5% faster than a 1660 SUPER, so I wouldn't pay much more than $240 for one. Pricing is not nearly that attractive though, and at $280+ currently, it's priced way to too close to a 2060 to be worth considering...
1660 Ti:
https://pcpartpicker.com/products/video-card/#sort=price&c=438