Will I have enough power and slots for this upgrade?

[afroman7600]

As you can see looking at my build below, I want to add a second graphics card, a sound card, and some memory to my system. However, I am concerned that I will not have enough slots, space, or power for my build. As configured on PCPartPicker, I am at 744 of 750 total watts on my PSU. Is this alright, or do I need to upgrade it? The builder does not seem to account for power used by peripheral devices.
Additionally, I am curious if I will have enough slots for this. Just looking at the numbers I do but, the GPUs are quite large and cover more than one slot on the board.
Lastly, does my processor have enough lanes to work with both GPUs and the sound card?

My Build

PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i7-6700K 4.0GHz Quad-Core Processor (Purchased For $329.99)
CPU Cooler: Corsair H55 57.0 CFM Liquid CPU Cooler (Purchased For $49.99)
Motherboard: ASRock Z170 Extreme4+ ATX LGA1151 Motherboard (Purchased For $151.13)
Memory: EVGA SuperSC 16GB (2 x 8GB) DDR4-3200 Memory (Purchased For $74.99)
Memory: EVGA SuperSC 16GB (2 x 8GB) DDR4-3200 Memory ($74.99 @ Micro Center)
Storage: Samsung 850 EVO-Series 500GB 2.5" Solid State Drive (Purchased For $154.85)
Storage: Western Digital 2TB 3.5" 7200RPM Internal Hard Drive (Purchased For $129.00)
Video Card: Asus GeForce GTX 980 Ti 6GB STRIX Video Card (2-Way SLI) (Purchased For $614.99)
Video Card: Asus GeForce GTX 980 Ti 6GB STRIX Video Card (2-Way SLI) ($649.99 @ SuperBiiz)
Case: NZXT S340 (White) ATX Mid Tower Case (Purchased For $62.69)
Power Supply: Corsair CX 750W 80+ Bronze Certified Semi-Modular ATX Power Supply (Purchased For $57.98)
Operating System: Microsoft Windows 10 Home OEM 64-bit (Purchased For $83.89)
Sound Card: Asus STRIX SOAR 24-bit 192 KHz Sound Card ($99.99 @ B&H)
Monitor: Acer XB271HU bmiprz 27.0" 165Hz Monitor (Purchased For $749.00)
Keyboard: Razer BlackWidow Chroma Wired Gaming Keyboard (Purchased For $134.92)
Mouse: Razer Naga Epic Chroma Wireless Laser Mouse (Purchased For $105.99)
Headphones: Razer Tiamat 7.1 7.1 Channel Headset (Purchased For $199.99)
Other: Bose Companion 5 2.1 Speakers (Purchased For $399.95)
Total: $4124.32
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-06-24 01:48 EDT-0400

 

[dark_globe]

your best option would be to sell your gtx 980Ti and buy brand new gtx 1080 .
corsair CX 750 is not really suited to power two power hungry video cards .
so you would have to replace it as well (more money invested) .

980Ti SLI is just not worth it anymore because now you can either SLI 1070s or get the 1080 .
both solutions are much more power efficient compared to 980Ti SLI .