Hello Sam,
1) The differences are the Epic and Orion are set
neck basses and the Essence and Persuader are
neck through. They also have different
electronics. Here is the
Bass product page. You can customize any of the
models.
2) There has been a lot of talk on wood. It is
best to search to find the threads. In general
the type of neck and body woods on a set neck
have an effect on the tone. For a neck through
instruments the neck woods have the most
effect.
3) I have an Orion 5 string and a 4 string
fretless (See April, 2006 FCTM). When I first
got the 5 string I found the neck to be very
close to my Jazz Bass in feel. I have had no
problems switching between them.
4) Can't help alot on the combo. My main rig is an
Eden Navigator into a Bag End ELF-M2 into a QSC
PLX3002 (or PLX2402). These drive 2 - 18 and
1 - 2 X 10 Bag End cabinets or 2 - 15 JBL and
one generic 2 X 10 cabinets. No ELF for the
15's just he the Navigator crossover. I do like
the Eden preamp and would suggest you also
consider an Eden Metro.
Keith