Vital Upgrades:
Tali upgrades the shields.
Jacob upgrades the armor.
Good but non-vital upgrades:
Samara increase fuel capacity to 1500.
Miranda upgrades the mineral scanner.
Thane increases the probe capacity to 60.
As for your Prima guide, yeah I believe it. I have one for Knights of the Old Republic II by Prima and it has information listed in the wrong places (e.g. one upgrade's stats under another's heading).
and don't forget about the "BIG GUNS" upgrade from garrus