I have owned a large number of cabs with various speakers in them and I believe that it takes time to determine the ideal matching of speakers (FL versus RL), cab, amp, and pickups.
I did sell off all my cabs (Marshall, Diezel, ENGL, Mills Acoustics, KSR, Bogner, Fryette (I probably missed something here, lol)) except for the cabs I have owned the longest, my MESA "Stilletto (the smaller rectifier cab)" 4x12 with 2 V30's and 2 EVM 12L's since they had the best tone for me (possibly due to using them the longest so my ears now prefer this combination). I pair it up with a 1x12 Mesa cab and I am able to turn the volume up or down for each cab due to a stereo mixing with my power amp. This might also be the determining factor for me since I can turn up the preferred speaker/cab in this setup.
I had many of the Diezel cabs and they did sound pretty good but I believe they are better matched with Diezel amps, and I thought I liked the earlier cabs that were made out here "slightly" more, but it might have been due to being broken in where the others had no play time on them and that can be a major factor since new speakers can sound a little harsh and lack that sweet spot until broken in.
One cab I did always consider purchasing again was an ENGL XXL FL cab.
It sounded great but when it arrived to my home I found that UPS had dropped it at some point and had torn off a large strip of tolex on the top so I returned it with the plan to repurchase it again, however, prices went up for it and I had just done the swap of 2 V30's for 2 EVM's and I found I really liked the way the cab was sounding with my current equipment.
One thing you could try doing is determining what cab/speakers sound best with your amp and pickups.
A good way to do it would be to connect a Two Notes Live or Studio to your amp then try to find a cab and speakers that stand out to you then see if the real one works the same way for you.
Also, every amp, cab, and pickups work well for different things.
For example, you might like one setup specifically for your rhythms where it doesn't work as well for leads or cleans and vice versa, so trying your current setup through a Two Notes might help you.
Well, good luck, since most of us know what you are going through right now
