Ok listen, there are USB adapters out there that work. Just because the box says PC only does not mean they will not work with the Mac.
For example when Circuit city went out of businesses they had an EVGA branded USB to DVI adapter. Regular price: $79...I paid only like $12 for it. I bought it and still haven't used it. (I already have a 24" monitor hooked up via displayport, so I don't really have the need (or space) for another display just yet) And I bought this adapter BEFORE I bought my MacBook Pro. I went down in my basement to find it one day after I got my Macbook and was disappointed to see that the box says Windows XP and Vista only. HOWEVER, I googled the model number and found that there ARE drivers for the Mac, you just have to download them.
So do the research if you are really that interested. There are many adapters out there that will do 1920 x 1200 on DVI that work with the Mac, you just have to find them.