Radeon 3450 or 4670 - XP versus Vista & HDMI output

Hello, I have tried to research this topic and am a bit lost and could really some fairly low tech help.

I just purchased a Dell 530 desktop with a fairly good processor Q8300 2.5GHz with 4MB memory that came with a 24" HD-1080p, LCD monitor with HDMI input. However, the intergrated graphics card is NOT HDMI compatiable and in fact doesn't have any memory. I'd like to upgrade this to a new internal card. I have seen much discussion on HDMI outputs versus DVI with adaptors. I didn't have the option to upgrade the card at the time of purchase, but see that Dell's recommended upgrades for this model are ATI Radeon 3450 256MB or ATI Radeon 4670 512MB. I don't do any gaming, but do some video editing and want to use the monitor as a TV and thought I should shop for the ATI Radeon 4670 512MB. When I started shopping I quickly found way too many brands and options. Also the better TV tuners want dual DVI inputs on the video card???? FYI - I have to continue using XP due to business reasons and it looks like Vista wont be on this computer for a very long time. Most the cards I looked at say the OS needs to be Vista. Is this true?

Wow with all that information, could anyone suggest a reliable brand and model that's in the $75-$100 range? Or is that too cheap for my needs? The computer has two PCI, one PCIe x1 and one PCIe x16 expansion slots