There is currently no way of using a Cinema display (transparent or silver) as a high def disaply with an XBox 360. The reason being that apple removed the analog portion of their DVI connector for a pure digital connection.
One company is about to release a box to market which basically decodes the whole image and reencodes it all fast enough not to see screen lag. Its going to retail for around £300 so pointless. The circuitry and processing required to handle it realtime is expensive and complicated so dont consider trying to make your own (I looked into it as I have access to almost every microchip on the market (and some that arent), decent fabrication facilities and can handle a soldering iron with a bit of skill and it was far too much effort and going to cost around £200 to make in discounted components alone).
It is doubly annoying to note that the exact same panel (cheaper too) from Dell includes the needed analog circuitry in the screen plus additional component connection to remove the need for a special lead from Microsoft.
I have an XBox 360 and a cinema diaplay and a 360 and hoped to do exactly this. Needless to say I searched high and low and it cannot be done. Apple f**ked up by giving us yet another propriatary version of DVI which just misses out all the normal DVI pins and decoding circuitry required. Your new cables wont do what you hope unfortunately
Coincidently a VGA -> DVI connector can never be high def as you cant get the info needed for high def out through a VGA connector.
finally Apple cinema displays cant handle resizing properly so even the low def signal you can get into them when running them as a TV will be distorted.
