First, we have the RC/RS400. The RS400 is the high-end dual-channel version, while the RC400 is a single-channel solution. Performance of an integrated graphics solution will suffer on the single-channel solution, of course, but for most businesses it really does not matter. Remember that the next version of Windows, codenamed Longhorn, will require DX9 graphics support, so these ATI solutions will meet this requirement. The RV370 core comes from the X600 chip, which is really just a PCI Express version of the 9600 chip.
That may not sound like much when compared with the latest X800 XT graphics cards, but when compared against competing integrated graphics that offer lackluster performance at best, it is not that bad. Radeon 9600 Pro cards are still capable of running all current games, although they may have to drop to lower detail settings to maintain decent performance in the latest titles. The RS400 IGP is said to be almost twice as fast as the 915G IGP, and it has the same drivers as ATI's desktop cards.
More info about ATI's upcoming motherboard chipsets over at AndandTech