What powersupply for this build?

[Whumberstone]

So i have ordered this system and its currently in pre-production

Processor (CPU) Intel® Core™i5 Quad Core Processor i5-4460 (3.2GHz) 6MB Cache
Motherboard ASUS® H81M-PLUS: Micro-ATX, LG1150, USB 3.0, SATA 6GBs
Memory (RAM) 8GB HyperX FURY DUAL-DDR3 1600MHz (1 x 8GB)
Graphics Card 4GB AMD RADEON™ R9 380 - DVI, HDMI, DP - DX® 12, Eyefinity
1st Hard Disk 250GB Samsung 850 EVO SSD, SATA 6Gb/s (upto 540MB/sR | 520MB/sW)
2nd Hard Disk 1TB 3.5" SATA-III 6GB/s HDD 7200RPM 32MB CACHE
Power Supply CORSAIR 550W VS SERIES™ VS-450 POWER SUPPLY

Now however i want to upgrade my GPU to a R9 390. I did a check on Coolermaster Outervision Power Supply Calculator and it quoted my build would have a load power of 470W and a recommended power of 520W. However PC Specialist says i will need a 650W powersupply even though the R9 380 only requires a 450W PSU.

Would it be too risky not to buy the 650W? the difference in price is £20 which for these base level PSUs is quite a lot

 

[jerpers]

I'd go for the 650w, it also means that it will be longer before the fan spins up, keeping it quieter.

 

[SpyderTracks]

I'd go for the 650w, it also means that it will be longer before the fan spins up, keeping it quieter.

If you go for the 650, go for the CS series as it's modular and made of better components.