Minimun cranking amps to start with jump starter?

[zensius]

Hey guys. I'm looking at buying one of those self-contained, jump starter/ power inverter things. I was reading reviews online and some people were complaining that they weren't powerful enough to jump start their vehicle. This kinda makes the thing a pointless purchase. So can anybody tell be the minimum amps that WOULD start a '92 automatic with a stock engine?
Does anyone have a recommendation for a model of jumpstarter that they like?

 

[biggs92EB]

i bought a cheapie from kragens that has fired my ex many times, but i always had some juice still in the battery, dont know if it has the power to start it from dead.