Personally I don't like to rely on panning to achieve instrument separation. Your mix has to have clarity in mono as well. 

EQ automation can be better than sidechain compression when there is a time range that is clear like vocal verses.

Not only do sidechain FX go in and out, the effect is soft when the feed channel is soft. You may need the opposite.

So creating a notch frequency and an envelope to control it, you can dial it in fairly fast aging automation nodes and dragging the range.

I have only worked with budget preamps and I'm wondering: does high end preamps (f.ex. 1073 which i would like to buy next time) help for better separation? I imagine the cleaner the sound, the better you can hear the individual tracks?

pilutiful
I have only worked with budget preamps and I'm wondering: does high end preamps (f.ex. 1073 which i would like to buy next time) help for better separation? I imagine the cleaner the sound, the better you can hear the individual tracks?

Short answer is no, your gear is not holding you back here.  This is all technique.  Check out Graham Cochrane's videos where he records and mixes a song on Focusrite Solo and a $100 LDC mic.
 
Also, you say you are working on a dense mix.  A lot of times commercial mixes that sound really dense, aren't as dense instrumentally as you think.  They get the density through EQ and effects.  As mentioned before, every instrument in your mix should have a purpose - not just be there to take up space.

In my post I was mainly talking about the highs.  I have said many times, if many of you with your dense mixes and things were to engage the services of a great producer what they would be doing is in fact removing half the stuff you actually have in your mix!  Most of it actually does not need to be there or if it does then it can wait and step in when other things are not stepping in.  Hence leading to this very accurate statement:
 

dwardzala
 
Also, you say you are working on a dense mix.  A lot of times commercial mixes that sound really dense, aren't as dense instrumentally as you think.  They get the density through EQ and effects.  As mentioned before, every instrument in your mix should have a purpose - not just be there to take up space.

 
The whole idea is to not get most parts actually even stepping on each other at all but weaving in and out of each other instead.  Many great commercial mixes are actually doing this all the time and there is far more space in there than many think.  But it sounds big though.  (less is more kind of thing)  So when stuff is not even playing at the same time as most other stuff, the good news is you can actually go back the other way and EQ for a fuller sound (and NOT have to carve out space for other things at all)  because you know it is not going to be playing that often at the same time as other things are.
 
There used go be three stages to a production. Tracking, mixing and mastering. These days there are four now. And they are tracking, editing, mixing (and more editing!) and mastering. The editing stage can be as long as any of the others too now.  Its OK to over track for sure and great to have a little too much going on.  But the trick is to let go a lot of stuff and only keep the important stuff that actually makes the statements you are really after.  Everything else is fluff!
 
This is also why some engineers like to commit early and make these kind of decisions early on.  The best live bands are also playing like this too, not stepping on each other.  They have worked it all out before hand.  British engineering is very much like this.  It is the Americans that started recording way too much and without effects and sorting it all out later.  Yes, more options for sure but more work sorting it all out.  
 
 
 

I have said this before and I'll say it again: I love these forums. Learning so much. Greatly appreciated.

That whole "weaving parts in and out of each other" is a breeze if you're doing it with MIDI programming via the piano roll. You can see all the tracks in question on the same roll, and arrange them visually. Great for programming a kick and bass that don't step on each other, for example. And you can get really creative with it. For instance, you can fashion melodic lines across two or more instruments, with each instrument taking it in turns to carry a note (a bit like the intricate weaving lines that African soukous guitarists play).