Gday all.

Im looking at upgrading/re-doing the 'radas audio, I've spent too much time around audio quality nazi's and I've become too used to high quality sounds :P

Basically, for ~$1500-$2000, what could I be looking at, in terms of headunit, and the 6 speakers all up ('96 KE Ei)

I trust you people!

6 speakers all up, does that mean 3ways up front, or 2ways and two subs?
If you're going to do all the install work yourself, you should be able to reach a good quality level within that budget, but as you get pickier you will find yourself spending more and more.
If you're going to be critical about the sound, you really should listen to the speakers installed in peoples cars (re: mea sound comps) to get an idea for how things sound, everyone will tell you something different ;)

but have a listen to your dyns, morell, mb quart, rainbow, hertz, oz audio, stuff all have good ranges, but you'll find a correct install will be a big benefit to how your car sounds

Edit:
Considering i was kind of in your same shoes, i'll give you a run down on what i've got for reference;
Eclipse CD000 head unit,
Rainbow Profi CS 265 splits,
Soundstream Tarantula TR 500/4 amp,
Qmax 6" subs (x2),

Soundstream Tarantula SST6.9 rears. - currently not plugged in (dont waste money on rear speakers)
Soundstream Exact 12" sub, - currently not plugged in, waiting to get a monoblock to use with my qmax subs

Would you recommend a DIY install job, or get a pro to do it

DIY if you know what you're doing, i started paying someone to do it, and have learnt bits and pieces along the way, paying someone to do it is an expensive process, remember to include wiring (at least 4ga - about $10 p/meter) and sound deadening (depending how crazy you go anywhere $300+)
Keep in mind the enclosures you have your speakers in makes a difference, so the sound deadning in your doors helps alot, same applies for your sub box, you need a good tight box ;)

you need a good tight box ;)

now THAT is essential for us blokes.....:bowrofl: lol

ahem......next comment.....

:spam:

lacking in the down stairs department eh ;) :P