AMD 850 / 256MB : $50 odd dollars (or less, i cant remember now) (runs asterisk)
SPA3102 : $195 (connects asterisk to VFX)
Tony, why do you need an ATA to connect asterisk to VFX? Why can't you just log on to VFX from asterisk? Is there not a UA in asterisk that will do this?
I am new to asterisk and I am thinking of doing something similar to what you're describing and I'm puzzled by this.