As the title states, I pieced together my first desktop gaming PC in 2012, after taking some advice from both here as well as from a tech forum. Over the years I replaced a few parts here and there; some from necessity, others for better performance. My CM Hyper 212 Plus heatsink just died on me the other day, which will require some effort and mobo-removal to replace. Which got me to thinking, would it be worth it to just go ahead and upgrade everything and/or build a brand new PC? Listed below are what it's currently comprised of:

Case: Cooler Master HAF 932 Advanced Blue Edition - ATX Full Tower; bottom-mounted PSU, 1x 140mm rear fan, 3x 230mm fans (front, top, side) (love this thing; gonna keep no matter what else gets replaced)

CPU: Intel Core i5-3570K Ivy Bridge Quad-Core 3.4GHz (3.8GHz Turbo) LGA 1155 77W

Heatsink: Cooler Master Hyper 212 Plus (no longer works)

Motherboard: ASRock Z77 Extreme4 LGA 1155 Intel Z77 HDMI SATA 6Gb/s USB 3.0 ATX

GPU: ASUS GeForce GTX 650 Ti BOOST DirectX 11.1 2GB 192-Bit GDDR5 PCI Express 3.0

RAM: CORSAIR Vengeance 8GB (2x4GB) 240-Pin SDRAM DDR3 1600 (PC3 12800)

PSU: Rosewill CAPSTONE 550M 550W Modular Power Supply (80 PLUS GOLD Certified)

SSD: Crucial MX100 2.5" 256GB SATA III MLC

Monitor: LG 34UM67-P 34" Class 21:9 UltraWide IPS FreeSync Gaming Monitor

OS: Windows 7 Home Premium SP1 64-bit


Some notes/questions:
-I'd prefer Intel over AMD
-Should I go ahead and upgrade to Windows 10, or wait until closer to 2020 when Windows 7 support ends?
-If/when I do go to Windows 10 (and/or if I replace the GPU), should I bump my RAM up to 16GB? My current mobo, if I keep it, can support up to 32GB.

Thanks in advance for any and all help and suggestions.