More than one extra Monitor - iMac

Hi

I currently have one 19" Samsung monitor connected to my iMac via the Mini-DVI. I am looking to get another monitor hooked up, but of course there aren't any more video ports.

Are there any alternatives? to have two monitors connected to my iMac? I have heard of the DualHead2Go product, and possibly connecting via USB?

I would appreciate any help on the matter, any info on the above and if there are any other methods. Thanks.

USB to DVI:
http://reviews.cnet.com/graphics-cards/tripp-lite-usb-2/4505-8902_7-33428157.html

There are lots of different ones, just an example.

DualHead2Go:
http://www.matrox.com/graphics/en/products/gxm/dh2go/#close


Would to hear some opinions on these products. Also, do you think it would work?

EDIT:

Ok so I now know that the DualHead2Go will work.
http://www.matrox.com/graphics/en/support/compatibility/gxm/

Yep. I went through the compatibility thing and it says im supported. Im just wondering of there is a cheaper alternative?