quickymart:

 

Would I need a new PSU for this setup, or would my existing one do the job?

 

Edit: just checked and apparently it's a "Cooler Master MWE Bronze 450".

 

Presuming that the "450" means 450 watts, that should be fine.  Newer hardware usually uses less power, but you are increasing the RAM which offsets that.  However, it is likely that the existing system is operating way below 450 watts anyway.  As an example, my MythTV box with 6 hard drives, two 8 tuner PCIe cards, an Nvidia GT 1030, and 8 Gibytes of RAM typically draws around 120 W when playing recorded TV programs for me (as reported by its Corsair RM650i power supply).  The only reason it has such a big power supply is that I wanted a modular one (plugable cables) and high efficiency (80 Plus Gold certified), both of which were not available in 500 watt or smaller power supplies at the time.  Here is what it reports at the moment (it is pretty much idle):

root@mypvr:~# OpenCorsairLink --device 0
Dev=0, CorsairLink Device Found: RM650i!

Vendor: CORSAIR
Product: RM650i
Firmware: NA
Temperature 0: 47.86 C
Temperature 1: 37.62 C
Powered: 144050977 (1667d.  6h)
Uptime: 245377 (2d.  20h)
Supply Voltage: 230.00 V
Total Watts: 96.00 W
Output 12v:
        Voltage 12.16 V
        Amps  5.00 A
        Watts 56.00 W
Output 5v:
        Voltage  4.94 V
        Amps  4.50 A
        Watts 22.00 W
Output 3.3v:
        Voltage  3.31 V
        Amps  3.88 A
        Watts 13.00 W