As far as the Jem goes it is a matter of quality, it's just the next level up from the Prestige (although the wizard neck on the Prestige models are th esame quality IMO). I know it's a small thing but they monkey grip is just so damn useful - every guitar should have one. The necks are also extremely comfortable and the tremelo system is amazing (deep set in a tiger claw cavity). They just have htat rare feel that when you pick one up you immediately think 'this is an amazing guitar'.
Re the pickups, I'm just speaking from experience and a lot of obsessive reading on Ibanez in general. Evolutions are what you will find on a lot of professional guitarists setups - Vai for one uses them bridge and neck. Having had a set on a previous Ibanez I can say they are amazing. Really sensitive and tight - no background noise yet excellent for picking up controlled feedback. Also very good for harmonic whammy dives (a point that most pickups fail on). Play a set before you go with them though, they suit a certain style, very hot - all of your mistakes will be laid bare! This will only force you to play better though;-) Nver heard of D Activators, I usually go with something tried and tested and always check them out in a shop fiorst. My 'Bad Horsie' Jem came with Breeds, very impressive and very unique feel - a great buy IMO (very different to the Evo's - more bluesy and 'thick').
Let me know what you get!