[WoW] 6 boxes increase to 10 boxes on MAC PRO (hardware upgrade)

Hi everyone,
Currently i'm playing 6 boxes (1280x720, mid quality on main, low quality on alt, just OK smooth).
If i only upgrade the SATA to SSD( intel SSD 520 series 240GB) for boot drive, is ok to handle 10 boxes (1920x1200, high quality) ??
Or any other suggestion?? (i'm sure i won't buy a new machine for gaming.)
thank you guys for help.


Here are my machine spec:

Model Name: Mac Pro
Processor Name: Quad-Core Intel Xeon
Processor Speed: 2.66 GHz
Number Of Processors: 2
Total Number Of Cores: 8
L2 Cache (per core): 256 KB
L3 Cache (per processor): 8 MB
Memory: 16 GB 1066 MHZ DDR3
Processor Interconnect Speed: 6.4 GT/s


Caviar Black WD2001FASS ( 2 TB ) x3


ATI Radeon HD 5870
VRAM (Total): 1024 MB


Displays:
LED Cinema Display:
Resolution: 1920 x 1200
Pixel Depth: 32-Bit Color (ARGB8888)

LED Cinema Display:
Resolution: 2560 x 1440
Pixel Depth: 32-Bit Color (ARGB8888)

Cinema HD:
Resolution: 1920 x 1200
Pixel Depth: 32-Bit Color (ARGB8888)

[MiRai]

An SSD will not increase your FPS beyond what your GPU can handle and I doubt you could 10-box comfortably with only a 1GB video card (looks to be your weakest link).