Went around Sim Lim and got some good quotations as well as a feel of what exactly is available.

Graphics Card (Quad output)

ATI HD3870×2 – S$559

Leadtek Quadro NVS440 – S$899

Matrox QID LP - S$1699

PNY NVS440 – S$899

(The most expensive)

Leadtek Quadro FX3450 – S$2399

I also found some VGA to RCA converters (about $70 each but there should be a cheaper one), VGA Splitters – 1 split to 4 ($90). There are RCA splitters as well.

Detailed information on analog cameras.

A high resolution Sony CCD Camera (Dome shaped) has 2 models, one for $149 and one for $199. The most expensive one is for $500, but that is probably too high end.

We have to bear in mind that with a quad graphics card, there might be potential issues of heat buildup in the computer as well.