The guitars without pickups will need mics. The ones that have a pickup but no preamp might benefit from an external preamp, not just a DI. At a minimum, make sure they get a DI with a very high input impedance, like 10 Meg for example. Higher than 1 Meg. The guitar with a preamp is just like an active bass, and will work fine with any passive DI (often a little cheaper than active ones from the same product line). http://www.musiciansfriend.com/direc...rrencyCode=USD
If it was me, I'd save up for around the $100 mark per unit, maybe looking at the dbx models. But as you can see there are plenty of Behringer, Nady, Rolls, and ART options within your budget. Heck, the Behr DI20 covers two channels for $25.