I have the 2.5Ghz with AMD Radeon HD 6630M andn have upgraded the RAM to 8Gb (Crucial memory) I use it almost exclusively as HTPC with the HDMI going via an Arcam Solo Movie 5.1 amp to a Samsung HDTV. The TV source is an Elegato Diversity and I run the latest EyeTV software. I noticed that on some TV programmes there can occasionally be a sort of jerky video stutter, not all the time and seemingly random. At first I thought this might be down to a poor signal to the Diversity but the reported signal strength is 100% at all times and signal quality ranges between 60-70%. However I tested the Diversity on my iMac to be ceriian and there are absolutely no problems. I've got the Diversity running in Diversity rather than twin-tuner mode. Then I noticed that there is the same jerky video problem when watching ripped DVDs (via FrontRow from full quality ISO images) and also sometimes on iTunes downloaded movies. This occurs less frequently than when watching TV, but it does happen. The jerkiness is not restricted to fast-action sequences but can occur, for example, on sequences like people walking across sets &etc. Anyone have any ideas?