my computer is a 950mhz athlon oc'd to 1ghz my second is a 750. both are stable and fast. i have a p4 mobo but havent seen the need to set it up yet
a well setup and maintained system with 700mhz cpu and decent amount of ram is as usefull as most systems ive seen my freinds and family using (i should know i fix and upgrade them for them)
btw an athlon wouldnt fit in an a1000 as there are no mini-itx mobos for them most have the new via cpus. those are capable of emulating an amiga though.