Oh dear, lets start with the basics...

1. what alloy?
2. do you mean a workpiece of 25cm x 25cm (you only said 'wide').
3. what do you want to do, engrave the surface or cut full depth pockets/holes?
4. where is the machine going to be used, in a workshop or a spare room
5. how quickly? Is a 24hour run going to be an issue?
6. whats your budget?