Sounds like you are getting a 7 string Carvin

. I love my Carvin, but people do tend to not like the pickups. First, give the stock pickups a chance. If you decide you want to change pickups, I would also recommend swapping out the volume and tone pots. Carvin uses linear taper pots for some stupid reason - you want audio taper pots. Also note the Dimarzio recommends a 500K volume and a 1M tone pot (that's the setup that they base their tone ratings on) so I'd go with those values.
For your possible pickups choice, I think you would find the D-Activator7 in the neck too loud with the d sonic 7 in the bridge. It is rated at almost the same mv output and leans towards treble (as a neck pickup should, but that will make it seem louder). I like the choice of the d sonic 7 in the bridge, but maybe you should match it with the liquifire that it was designed to accompany. You could go the D-Activator7 route, but you may have to back it off a bit more from the strings than you would otherwise.