Conclusion
Judging by the test results, you can indeed save on your graphics card in the time of economical crisis. As you could see, the CrossFireX tandem of two Radeon HD 4830 cards is generally faster than the single Radeon HD 4870, which also costs more. Therefore you can buy one cheap Radeon HD 4830 and then, half a year later, buy another such card to get a nice performance boost for very little money. Or you can save today by buying two Radeon HD 4830 cards as they will be cheaper than one Radeon HD 4870.
At the same time, you have to be prepared to certain difficulties and problems if you decide to go CrossFireX. Even if you are lucky not to have any problems with the installation of the driver and control panel, you won’t be able to avoid the problems in games. The jerkiness in Far Cry 2 makes the gameplay most uncomfortable, for example. There are image defects in 3DMark Vantage and Unreal Tournament 3. CrossFireX mode is disabled in Cryostasis: Sleep of Reason when you change the display resolution, and in S.T.A.L.K.E.R.:Clear Sky you need to restart the rendering engine manually to enable CrossFireX. Besides, a system with two Radeon HD 4830 consumes more power than a system with one Radeon HD 4870. If you are not scared by these difficulties, and you still hope for improvements in the next versions of Catalyst, the Radeon HD 4830 CrossFire configuration may be an appealing solution for you in terms of price/performance ratio.