With $200 you can get a 1.5TB WD
drive and 4GB of DDR2 800
with change to spare.
Yes, HDMI and DVI output the same video signal.
The only difference is that HDMI is capable of carrying an audio signal along with the video.
Using a DVI => HDMI adapter will output the exact same digital video signal just without the sound (unless you have a newer ATI GPU).
As your newer GPU already has an HDMI output, I would recommend using it.
IDK why the manual recommends using the DVI => HDMI adapter.
Perhaps the same manual covers several similar cards, some of which lack the dedicated HDMI port.