Loop expansion questions!

[wasteomind]

Hello, I need some help.

I currently have:

Pump = Swiftech MCP655-B
Radiator = The Feser Company (TFC) X-Changer 480ER radiator (4x120)
Cpu Block = Apogee HD
Reservoir = 120mm Koolance
Fans = 4 Yate loon D12SM-12 (120mm) in pull
Tubing = 1/2" (13mm) ID

The loop is configured as:
RES - PUMP - RAD - CPU - RES

Right now everything but the cpu block (obviously) is in an external enclosure I built. Currently this loop is running just the cpu. It was always my intention to add my gpus to the loop and so I'm wondering if the single rad is enough to handle adding two gtx 680s in sli.

I used that power calculator floating around and figure I'm somewhere around 500w of heat. I think 480 rads are good for around 600? Also if this rad does support the extra heat, how much of a temperature increase should i expect to see across the board? CPU idles high 20s to mid 30s and loads at low 70s. Gpus are currently air cooled with stock coolers so standard temps apply here.

PC specs (sig is not updated):

ASUS P8Z77-V PRO
INTEL I5 3570k @ 4.7ghz 1.275v
CORSAIR 8 GB (2x4gb) DDR3 PC17000 2133mhz 11 11 11 27 1.5v CMZ8GX3M2A2133C11R
2x EVGA GTX 680 SLI
Crucial M4 CT256M4SSD2 2.5" 256GB SATA III
Crucial M4 CT512M4SSD2 2.5" 512GB SATA III
Windows 7 x64
COOLER MASTER HAF 932
Thermaltake TPX-1275M Toughpower XT 1275-Watt PSU, 80 Plus Platinum Certified

 

[wasteomind]

Sorry to bump my own post but I reckon I found an answer to my own question about the temperature delta from this chart. Looks like I'll see an increase of around 8c if I'm reading this right.

 

[Cruiza]

I would say your existing rad/fan setup should definitely be able to handle your CPU and two GPUs. Could you get better temps by adding more rad? Sure, but it wouldn't really make a difference in anything other than max temps by a few degrees at best.