I could be wrong, but here is what I understand...
If you simply make a VGA cable and change the bios or whatever you will merely be displaying a TV signal on the VGA monitor. On a monitor's high resolution this might not look so great.
What you WANT to do is use the VGA monitor as a High-Def monitor, so you get a MUCH better picture.
There are 2 ways to do this RIGHT (if you get a TV to VGA converter, all it is is a crappy line doubler - you won't get the great picture).
1) get the X2VGA adapter. It will display TRUE High Def on your VGA monitor
2) Get the VD-Z3 adapter. It will also display TRUE High-def on your VGA monitor.
There are pros and cons.
X2VGA $65
Pros: You can still view the Dashboard, even though it is running at 480i instead of p. You just get half the dash at a time on your screen and have to scroll around, but you get it, and get it in color.
Cons: works for XBOX only
VD-Z3 $50
Pros: Can be used with ANY game console, even a Progressive Scan DVD player if you wish!
It's cheaper
Cons: it has a special mode that allows you to view the dashboard at 480i. However the con is that with this is that I think it is blurry and not so great looking.
Now heres the thing. The cons of both of these devices don't really matter. There is a hack posted in this forum (sticky post) that shows you how to change a single hex character to get not only the Dashboard in 480p mode, but it will also get the DVD player to display in 480p mode.
This means that with this hack, and EITHER device, you can get the Dashboard and the DVD player to display nicely on your VGA monitor!
That being said, the VD-Z3 seems like the better bet for you.
However, if you do not want to hack you dashboard file (a back up copy of it) w/ a hex editor, then you are better off with the X2VGA. Read the stick post on the hack for Progressive scan mode for the dash and see if you are comfortable doing something like that, and then decide.
Brain21