600mm cutting width is probably a bit of an issue, it pushes you up into the heavier capacity range of machines, all of which won't leave you much change out of $3500-$6000, for a fairly good one that is.
I'd have a think about what it is your trying to cut, and especially as your starting out then see if one of the cheap Chinese 3040 or 6040 machines would do? They will come with a crap controller most likely (search the forums for tb6560), so I'd recommend buying a Gecko G540 on top of the machine to really get some good performance out of it and just increase the overall reliability. The $300 the G540 costs might seem a lot, but it truly is an investment you'll appreciate almost immediately!
These machines are mass produced and marketed to a price point, and really aren't too bad at all once you scrap the rubbish controller that comes with them, and make some small, quality enhancing adjustments. As they are open ended (unlimited length materials) I'd suspect one of these would keep you happy for some time as it sounds like you'd be doing signs, and shouldn't set you back more than around $1800 all up, and will give you a greater experience of CNC as you go to make a more informed decision for when you want to upgrade later!
cheers,
Ian
It's rumoured that everytime someone buys a TB6560 based board, an engineer cries!