re: panels
Yeah GIK is one of the ones I considered, looking mainly at 2" 4x2 panels, maybe a couple 4" to "trap" more bass (I know that word can trigger some acoustic people!) I think if I get some I'll with Acoustimac, as they are in Tampa and shipping is very cheap to me.
re: reference tracks
There are some pro engineers that say don't use them. I do simply because I don't trust my own ears
I don't use them enough, they are getting old, and basically this isn't my day job. I don't think I'd go in with the notion to make your mix sound like the reference track exactly. I feel it helps with basic levels, with maybe giving you a "wetness" to shoot for, etc.
For your tune, I referenced to 7empest as it seemed reasonably close to your tune in feel and instrumentation. Now, whether it's close in production value....that's really a question! For example Jeff Lynne/Tom Petty decided to make Tom's vocals VERY dry on some of his later albums. Go back further, Journey's Frontiers album is the most verby album I've ever heard, there's tons of reverb on everything but it somehow works (IMO).
As I mentioned, Tool does some oddball (from the norm) things with their mixes. Bass usually has delay on it, guitars are always panned wide (matching yours!), Drums are quite centered other than the toms which fly around your head, and the kick is the loudest since Rush's Moving Pictures album or Heart's Barracuda! His snare also sounds like a small tom. But all that said, I still found it useful.
However, another use for referencing is to take a song(s) you know very well and use it when you are in a strange/new environment, or want to try out some new phones and speakers. Woman in Chains from Tears for Fears was one of my favorites. I'd use it to reference no matter what the song I was working on
And you mentioned you now have Metric A/B, which will let you queue up a bunch of tunes as references! Bottom line I wouldn't get too hung up on the similar song thing, that's kind of a bonus IMO. Obviously if you are trying to use Adele to help you with hard metal guitars or something that might not completely work, but it still could help just with overall balance, setting verb on a vocal etc.
Lastly in case I didn't put it in the thread previously this is a fantastic collection of multi-track projects that give tons of different songs to mix and mess with. I went looking years ago for free available songs to mix and this was beyond any hopes I had.
www.cambridge-mt.com
In fact, another forum I was on talked about maybe doing "contests" of a given song from this repo--not really to find a winner, more to see what everyone did and people could learn from the results. Just food for thought. KVR does this with composition for their "one synth challenge" contests and it's awesome to see the songs that result from the various participants.