Thinking of upgrading my pc

[derpholio]

so guys. i bought my pc 3 years ago, this is my current rig:

gtx 650 2gb
450w cooler master
i3 4160 3.6mhz
4gb ddr3 ram
gigabyte B85M-DS3H motherboard
derp case, kinda big.
1tb caviar blue and 200gb caviar blue

so as you can see, i cant really run popular and new games like witcher 3, mortal kombat x, battlefield 4 (actually tried with all of these), and i got unplayable fps on all of them.

so going to the point: i was thinking of getting a gtx 970 (not sure if i can sli this with my 650), an i7 4790k (Probably an overkill for a 970, but i'd like to maybe upgrade again in future, so im going with either this or a really good i5), 8gb ddr3 ram (if it can sum up with my previous 4gb) or brand new 16gb ddr3, and a 750w psu (maybe better) and an ssd (Not sure about anything for the ssd), so i wanted to know: will these fit in my motherboard?
how can i sli these two vcards? will the ram sum up if they have different frequency? is 750w enough?

pls help.

edit: almost forgot, my estimated price was around 1k dollars, i'm not looking for very expensive stuff.

 

[gskill support]

Def no SLI.

4690K and 4790K is as good as it gets for gaming right now.

DDR3-2400 will be good for first person shooters. Getting 8GB of a higher frequency may be better than low frequency 16GB.

PSU, there a 80 PLUS GOLD for really good prices. GOLD cert ones have to use quality parts to sustain that efficiency so theyre the ones to look at for high end gaming, not necessarily just a high wattage.

SSD, Intel has some specials going on, def worth it.

One key thing is motherboard, you'll want something nice like a ASUS Z97

All of the above would cost you much less than $1000. The best gaming system right now shouldn't cost you much more than this.

 

[gskill support]

Look something like this, you can play all those games on max like butter:

http://pcpartpicker.com/p/ZTV7Jx