http://www.tomshardware.com/reviews/ATI-Radeon-HD4650-HD4670,2444-8.html
Someone should get them to correct this article if it is indeed incorrect.
"For instance, in one of our office systems, we used to have an NVIDIA Quadro NVS 420 card, originally valued at $399, for displaying up to four monitors from one card slot. However, as we’ve made the jump to Windows 7 and our apps and usage has evolved, daily work was simply more than the NVS card could bear. We opted to replace the NVS with a two-slot solution: a Radeon HD 4550 and HD 4650 card. This gave us a dramatic improvement in graphics performance, let us keep support for up to four monitors (thanks to having two DVI outputs per card and ATI’s drivers that allow desktop spanning across multiple monitors), and kept the price tag down around $100. With a slightly different configuration, we could have used a motherboard with integrated AMD graphics and a 4650/4670 add-in card to achieve the same results, although we really wanted the extra performance of the 4550 above what an IGP could provide."
They seem to be implying that hybrid is possible with HD4000 series and the release of HD4200 on 785g mobos just adds to the confusion.
Anandtech also had an article which had such an error which they corrected however they left on that the HD4200 might work with some Evergreen GPUs which I'm skeptical but have no way outright telling them they're wrong as of yet. Anandtech's article in question is this one:
http://www.anandtech.com/mb/showdoc.aspx?i=3615&p=9&cp=4