Almost my same exact timeline. I also come from car audio basshead days, then got into headphones and shortly after started searching for pairs to satisfy my bass needs. I will tell you it was tough, it didn't take me long to realize most of headfi's opinion on massive bass differs greatly from my own. After purchasing 3 different sets of headphones that were all suggested to have STRONG bass, I finally found this thread. All of us in here seem to have a different take on bass than most of the general headfi community lol.
Because of this thread I found the SZ2000 and Fiio E12, and then my basshead dream came true. I now officially have the ultimate bass-can set-up, and I couldn't be happier. And now with the addition of my TH-X00's, I also have a "audiophile" grade pair of headphones that still deliver the thump, satisfying my basshead desires all while sounding amazing overall.
So thanks to HBB and others I have all my basshead needs covered for now....
JVC SZ2000: maximum impact and rumble
Fostex TH-X00: fantastic overall sound while still providing solid slam
Sony MDR-7550 IEM: portable basshead needs
Fiio E12: power and slam on the go
iFi iDSD: desktop power house, can go portable in a pinch
Now I'm debating if I want to get a more portable DAC/AMP combo as the iFi is too big to fit in my pocket. Right now I just stack the E12 onto my source, not using an external DAC. Don't have a large budget for this so I'm looking at the Cayin C5 Spark, Fiio E18, and Oppo HA2. Still undecided.