On the VIVO topic, I just got an Asus Radeon 9600XT for £140 with VIVO. The quality is fine and it's a very nice card although it is perhaps more than you need for what your doing, which isn't gaming. Still though, the VIVO capabilities are great for the price. Many Radeons have the rage VIVO chipset onboard, on a budget this is a good option to go for.
I'll back Mr ripling on the second hard drive advice too. One of the best things you can do for your system. Just buy a small one and install your OS on there and your programs on a seperate HD. You can never have enough physical hard drives, I got one for programs, one for swap file, one for OS, one for audio, one for video. Overkill? Naaah

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Also probably the best piece of advice I can give you, install a multi operating system setup. You say your kids wil be doing homework on it so I'd strongly suggest that you install one set of Windows (if indeed that's what your using) solely for editing use, otherwise I imagine you'll run into problems at some point. Partition your hard disk to have 1 partition for the boot sector, 1 for you editing OS, one for kids/internet etc. If this is all japanese and someone else is installing the OS, ask them to do this for you, it's not so hard.
Good luck
