Why would you want a monitor that uses VGA? DVI to VGA adapters do exist.
I suggest you look for monitors that have DVI connections. Since you card supports dual link DVI it will have no problem handling monitors with resolutions greater than 1920 x 1200.
Incidentally, it just popped into my mind that you may have been hung up on wanting a 1080p monitor just because you think it looks great on a TV with good resolution. You should know HDMI is not as good as even a single link 1920 x 1200 monitor. 1080p only has 1080 pixels vertical. Single link has up to 1200 and dual link has up to 1600 (2560 x 1600 resolution). Both of these are much better than HDMI and without all the connector aggravation.
I am a video editor. I am updating to HD after having worked in Standard Def. for many years. My new HD camera will be 19s0 x 1080 and I want a true video monitor, not a TV or computer moniotor, in order to do a good job of monitoring colors for broadcast purposes -- every tv is different, so I really should have a video monitor such as the Sony Trinitron SD monitor that I've used for ages but will not handle the new HD footage from my new camera. So, from everything that I've read, they tell you to get a monitor that matches your camera resolution, which is 1920 x 1080 -- the Sony is an inexpensive ($1100.00 -- cheap for video monitors) and should give me a start. So that's why I've chosen that one, but I'm willing to learn!
Then the only think I could suggest is use one of the adapters I mentioned with the monitor you choose. Make sure the monitor has a decent return policy. And give it a try. If it doesn't work, return it.
As suggested earlier maybe consider the 5770. I will work on your machine so long as you have 10.6.4 or greater installed.