Well being in the US be prepared to pay a pretty penny for A1200/600's... Even A4000's are costly. I have one of each.
Indeed. I always get jealous when I see European users posting about the 4 A1200s they got for 5 euros each. :-)
I paid almost $80 (incl. shipping) for an A600 from the UK, which is still a little cheaper than what they tend to go for locally in the US.
EDIT: Er, ahem, on topic, an A3000 or A4000 will probably offer you the most expandability "out of the box". A1200s probably have more potential, but they'll need to be re-housed to get the most out of them, which will set you back another couple hundred dollars for a dedicated tower solution.
