Need advice on my current loop

[Sickb0y]

First my current pc specs

i920 overclock @ 4.2 watercool
12 gigs of Sektor 7 DDR3 (6 x 2)
2 x 1TB sata
2 x 1.5TB
2 x 40 intel SSD drives in Raid 0
1 x 24x burner
eVGA X58 3X SLI mobo
Kingwin Mach 1 1000-Power PSU ABT-1000MA1S
2 x GTX480 1.5 (1 is an eVGA GTX480 Superclocked the other is a PNY GTX480 brand)
ASUS Xonar HDAV1.3 Deluxe 7.1 sound card

For watercooling I have a
Swiftech MCP655 with a EK Waterblocks EK-D5 X-TOP Rev 2
XSPC Rasa CPU (Acetal) Chrome waterblock
3 x 120mm single radiators

1. XSPC RX120 (the fat one)
2. XSPC RS120
3. Black Ice SR1 120

Water Tank Z-Multi 400 Reservoir
Danger Den single 5 1/4" Bay Reservoir

Picture of current setup (excuse the quality)

So my question is this I have a third GTX480 (eVGA brand) which is not install at the moment since I can't fit anything on the motherboard. However if I watercool it I can squeeze it at the first slot next to the cpu (will only take 1 slot away if i watercool it) and still have room for my Asus Xonar soundcard. Would it be o.k. if I throw third GTX480 on my current loop? I don't plan to overclock the GTX480 but the CPU will be overclock. Or should I add another radiator or split the loop?

I have some extra parts laying around
1 x MCP-355 with XSPC Acrylic top
1 x Danger Den Reservoir which is currently install on the system (top left) first 5.25 slot
About 5 feet of PrimoFlex Pro UV Red Tubing -7/16in. ID X 5/8in. OD
This was all left from a second loop I had when I had 3 x 5870

Any suggestions?
thanks

p.s. before someone mentions it the current PSU will be replace before I even bother installing the third GTX480. I know the current PSU would not be able to handle the load.

 

[Tsumi]

Yes, 3 120 radiators is enough for a CPU + GPU.

I'm not sure how good that 1000 watt power supply is, but if it can deliver 1000 watts, it should be enough for your system.