The blower version is a lot more expensive online, is there any reason for this? Also how much more is it worth investing in the 1660 over the 970?
For max performance, at this moment GTX 1660 Ti is the best option, very close to RTX 2060 without RTX on.
Blower version is the best option for X51 case and airflow setting, which could push the heat airflow directly outside the case. Heavy gaming would have graphic card generate a lot of heat inside the case. Cooling is a big problem to X51. The heat from from graphic card would finally and quickly affect the CPU cooling, making the cpu fan very noise and clock dropping. That's my experience when I was using gtx 970 with open fan design. At the end I had to open the side panel.
Open fan GTX 1660 Ti is acceptable since it was not too hot and "only" rated 120W TDP if you don't care the noise.
My exx loving gaming machine, X51 R2 i3 4130+6GB+GTX 645+240w -> i7 4790+16GB+256GB SSD+GTX 760+330w -> GTX 970
I still keep the gtx 970 3dmark FIRE STRIKE EXTREME scores here
https://www.3dmark.com/3dm/9993605
GTX 970 now is not that powerful for new heavy 3D gaming such like FPS, could not reach 60fps on 1080 high setting
Here is gtx 1660 ti scores
https://www.3dmark.com/fs/23536545 around 40% performance difference