What piece should I get next?

This is exactly what was thinking as I was reading your post.

Mix With The Masters. Ronan Chris Murphy does a destination Recording Bootcamp (that he actually started BEFORE MWTM started if I remember correctly).

I know, without a doubt, that I'm the weakest piece of gear I have. I'm trying to get better so I'll be better able to utilize with discernment my existing gear.

...also I need to get a nice condensor for vocals - the at4040 just isn't always doing it for me - but you've got that covered if I remember correctly!

What is it about the end result that you feel is not where you'd like it to be?

You've had some pretty good gear through there. I'm leaning towards maybe rethinking your approach to mixing. it's not really a fundamentals refresher, but a rethinking of what you are going for. I did the same thing a few years ago and I'd say it's pretty eye opening to start really doing stuff you'd think was crazy.

Some of the things I've seen differently is compression *amounts*. Folks will say "I put a little compression on it" when they really mean like 10dB+ of compression.. Or they'll say something like "I put a little 10K on the vocals" and they really mean like 15dB of 10K..

In other words, maybe try to forget what you've heard and just go wild for a while.

Or since you're in Nashville with a lot of great engineers/mixers, take some of the stuff you've done and go to someone else that has a sound more like what you want and ask(pay) them to mix it again while you sit and listen/learn. It's always interesting to see how someone else interprets things that you've become too close to.

Getting out of the box will certainly give you a new perspective.

I'm actually leaning towards it...although I could see keeping the Apollo...The 2x6 doesn't have the new ADDA does it?

As I said elsewhere maybe try something like ATC SCM25 three ways.

If you think the Burl added something your missing grab another.
I might try a outboard verb, say a used lexicon or something just to see.

I see it this way .....
If I have great gear there is a point where I just stop buying new gear and its time for Rock and Roll.
Who cares if its a little duller, or less detail. The Magic is in the song.

In other words the next piece I get is a piece of cake.... and I have to vacum clean the flat.*

Johnkenn - I think sometimes simple is best. We often look at "adding" lots of gear as we search for that extra mojo that will inspire us. I think simply focusing on your master buss might be a good area to investigate. I have tried many things there and the LTL Silver Bullet by BradM and drbill has me smiling these days. Bigger and more open sounding than my buss comps alone, and I can get that extra mojo without my mixes closing up. My goal on my Master buss is to keep things simple and try to not have things change. I want less things to fiddle with and focus on mixing and making music. I keep the settings the same as much as possible and then engage the EQ and filters only if needed or I would use the EQ for sweetening if mastering. Brad offers a no risk trial, so it's a no brainer to give it a shot. If you try it, I'd be happy to share my fav settings. In your situation, if you like modern production I'd try his regular silver version as opposed to the Void Corps edition. I too like to retain clarity and although I love analog mojo, I don't want to hear any smearing or hearing things get smoothed out too much. I've found a spot that balances between the API amp into the Neve Amp and it sounds pretty darn sweet. And to boot you can use it as a sweet stereo mic pre and it also has a great sounding bandaxall EQ and useful EQ filters as well.

Or for  lot less money, spend more time a/b -ing with reference mixes.

I've been reading A LOT about Billy Decker who is all itb. He never talks about hardware. Hell, I can't even find what converters he uses. He probably gets all kinds of mixes tracked on different converters. He'll send his songs to all kinds of different mastering houses who probably use all kinds of different converters. What he does talk about is a/b ing songs for reference , having a computer system that doesn't crap out, samples, and plugins. For his pro stuff he doesn't use anything other than an L2 on the mix bus. Of course he's sending his mixes to  great mastering houses, but I wonder how much they're actually improving his mix. I really don't know. When he self masters he uses an EQ on his mix bus and an L2. 

For his method: He's compressing and limiting the shit out of his individual channels and pulling down his master fader. He does a lot of low pass filtering on everything and mixes hot in the 5-10K range. instead of EQ'ing kick and snare he uses three samples of each- high/mid/low - and then parallel compresses the kick and snare on different channels with an SSL type plugin compressor.

I know everybody doesn't want to be Billy Decker, but you cannot argue with his success even though you may hate the type of temeplate based music he's mixing.

The guy never talks about hardware. Just an interesting counterpoint to gear obsession.

Lastly, his room looks very well tuned and has lots of wood, but he's using Mackie speakers. The guy could get any speaker he wants. 

Here's his mix tutorial. He uses a lot of Waves stuff and uses Trigger. If you look at some of his presets, you"ll see "CLA". Apparently he met CLA when he was in Nashville and CLA walked him through what he does channel by channel. 

Here's him posting from the purple place: He's had his share of #1 hits.

Anyone wanna buy all my gear?

I do.  How much?