What is the most decadent, most self indulgent--

Vinyl...LP's of all sorts, cost be damned. Multiple copies of "rare" LP's, I'm awash in vinyl. I love it, but truth be told I coulda bought the Porsche I lust with the money I spent on analog tunes. No regrets

Craig, you're absolutely right about LOTS of gear but in my own twisted way I can almost justify having so many set-ups. It's not self indulgent to have a tubed CDP in a garage system is it? Lot of relective surfaces in a garage, a man needs tubes in such a harsh environment! As for my bathroom system..well, some read in the "library" others tap their toes to tunes (from a sitting position). The outdoor system irritates my neighbors to no end, I suspect they're jealous cuz their mass-market rack systems in their living room can't hold a candle to my pool-side rig. I consider this a community service, allowing everyone around me a glimpse at a decent sounding stereo, enriching their lives as it were?
Honestly, I have a very hard time parting with gear (unless it turns out to be disappointing, then it's easy). Stuff gets swapped in and out of my various systems all the time to test synergy and can at times lead to some confusion. As an example, I moved my ML Aerius aside for a bit in my home office system and inserted my ProAc Tablette 2000's, after a little bit of time I had a tough time deciding which I like better. So, owning many different pieces of gear allows me to conduct all sorts of listening experiments. Keeps me off the streets.
We all know what happens to the value of audio gear, more often than not the cash offered for stuff just doesn't make sense to sell it off, at the prices things fetch I'd prefer to keep it than "give it away". As I've upgraded my two main systems, new systems were put together to a point I've honestly run out of ideas as to where to add more. Wait...I don't have a kitchen system! Everyone should have a kitchen system shouldn't they? Ah hah, a use for my extra Linn Classik!