Yup, we need to know the components in your current build in order to suggest any upgrades. How are we to know what RAM your system uses or if your GPU is AGP or PCI-E? A budget should also be provided. Is this a strictly HTPC, or do you perform other tasks with the build?
motherboard - msi k9ag neo2-digital
graphics - sapphire radeon hd 2400 xt with hdmi adapter passive cooling
memory - 2x mdt 1024mb ddr2-800 cl5 m924-800-16