Ok so I have 2 Sata III SSDs a 240 corsair force 3 240gb as my main boot drive. Also have a 480gb SATA III game and back up drive. And I ran out of space. To many pictures and 3-4 games and the drive is full.

Several choices
Another Sata drive into a slower port for the games.
Or
Buy a pcie to M.2 adapter, Amazon has a decent one for like 10 bucks or for 20 it has 2 m.2 slots one for nmve and one for sata.
Plug that into my pcie slot and go.
Drive options I am looking at is the Intel 660p 1tb for $100. Yes its QLC but I only need to write once play the game and maybe in a year get another and write again. I know it has low rewrite but we are talking about 200tb which is filling the drive 200 times, never going to happen

So the question is which is the better option? Cost diff is maybe 15 or 20 between sata 1tb and this Intel drive.
Will it work in the pcie slot which I think is the 8x because it's the 2nd out of 3 in my MB?

Anyone have any better options I havent though of. Keep in mind trying to keep cost down as much as possible.

Thank you all for any help!

My 670 is sitting in that slot folding I wanted to give more room between the 2080 and the 670 for airflow.

So wouldn't it be better to use the nmve adapter and a 1tb drive. It seems to be faster by about 2.5 to 3x. And I dont have any more SATA 3 ports so I have to use the slower SATA 2

if you have an NVME adapter and M.2, you can satisfy your application and in the future, take that M.2 to a new motherboard with a dedicated M.2 slot.  that's what I would do.   

Replace your existing gaming 480 (your full drive) with the biggest SSD in your budget.  Then move that 480 to replace one of the 240 (Boot Drive)
 
Now you'll have a nice 240 to make a portable drive if you buy a case.
 
Time to Update your signature ---> 2080

xshurikx
I see the consensus seems not to go nmve, interesting. I guess with the next build I can go nmve. But that is years away as I really barely game anymore. Been a year until today. But extra space is needed for the future always

It is just that You pay a premium for M.2 NVMe
 
Is M.2 Faster - yes.  Will you see a Huge difference Gaming (FPS) -- unlikely -- bench marks Yes