Unless we are supremely lucky, all of us have regrets at some point in our lives.

Specifically - Which piece of equipment or software do you most regret having sold, given away, etc.? Why did you do it? Did you ever do anything about it?
A pair of Klipsch Heresey's. They weren't doing me much good in the garage. These were the older Heresey I. I thought they were much better than the newer models. Now I wish I had them for my son. They couldn't be hurt and they were great for rock music. (although they could hurt his eardrums I suppose)
Duane Allman's Marshall 100 amplifier. (I'm not kidding). That amp had the classic late 60's Allman, Hendrix , Clapton sound, but was too powerful for the clubs I was working in at the time. The ability to attenuate was not perfected then, so I bought a smaller Marshall 50 Watt combo. Worse than that, I gave an ex- girlfriend one of Jimi Hendix's hand made leather ponchos, which was given to me by his manager just after he died. Needless to say, we are no longer together, and the poncho is long gone. Must be worth 10 grand by now.Damn!
Sold my Apogee Duetta II speakers for next to nothing because I thought one of my kids would put their hand(s) through the ribbons. Damn I loved those speakers, driven by gobs of Classe current and a great analog front end. The nice thing about the 'net is it open up new avenues to acquire hard to find items, I know if it bugs me enough there's another pair out there with my name on 'em
I regret giving a custom framed, unopened, original copy of Sgt. Peppers as a wedding gift. It wasn't appreciated. I never received a thank you note. The bride allowed her child to open it. The marriage ended quickly and that precious piece of history was thrown in the trash. Color me heartbroken.
Sold my Fisher 500C receiver in the early 1970's to buy a Marantz 2270 receiver. Sure wish I had kept my Fisher...
While I was away my wife and daughter had a garage sale in preperation to moving...They sold a set of Kenwood Audio Purist LO7M monoblocks, LO7C pre-amp, LO7T tumer, Ariston R11 turntable, Thorens TD 125 table, SME3009III tonearm with three wands with Sure V-15, Ortofon MC and a John Marovkis MIT MC cartridges, all in working order for $150!
Oh well........Lovesmusic
A pair of Stromberg Carlson folded horns in immaculate condition with SOLID (not veneer) rosewood cabinets. Sounded like crap but antique furniture to die for!

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My 1955 Chevy Nomad station wagon. I know the sound system was not all that great, but the container has become a classic.
Probably the original Beatles albums I bought in 1965. I'd also like to have the Shahinian box speakers for my second system I sold 13 years ago & my old 1969 FLH.
Had to sell my Accuphase P-300, C-200, T-100 to pay for books and tuition during college. Overall, a very good investment in the long run, but I really do wish I still had that fine equipment.
I wish i would have stopped messing around with one specific system when i had it sounding "right". It sounded phenomenal on all types of music and had really excellent "PRAT". Being the "boy genius" that i am, i kept monkeying with it trying to "make it better" and i've never been able to get it back to that point ever since. I'm sure that i'm not alone on this one though, but it's still not much of a consolation... Sean

PS... Viridian, you read my mind : )

Selling all my albums.I had 2 trunks of master recording in mint condition and sold them dirt cheap when CDs came out.BAD MOVE!
Old Quads, Servo Static, AR D-150 and D-79. Wished I still had them.
Overpaying for a compact disk player,live and learn.
Many regrets selling my Berning EA-230 tube amp and Chartwell LS3/5a speakers. A magical combo!
Quad 53s, Rogers LS3/5A, an old Jadis amp. Like Pragmatist, paying giga$ for a cdp.
Two years ago during spring cleaning I threw my Dad's old Sansui 1000X receiver into the dumpster. This was during the early stages of my becoming a devoted audio enthusiast when I was more interested in the latest gear and what my next upgrade would be. I grew up listening to this old workhorse, and my love of music reproduction blossomed because of it. The unit wasn't working perfectly and was in need of repair and refurbishment. Now that I've become a hardcore audiophile when I think back to that tragedy two years ago, I feel like having someone kicking me in the balls over and over. Really hard!
I regret giving up my old Altecs but I did keep the instructions that came with them. See

I remain,
My original Quads with Decca ribbons - replaced with Vandersteen 2Cs. Giant step backwards. But what I really wish I still had was my '67 Z-28 or my '40 Willys. Don
A pair of '36 Fords, a blue coupe and a black/red convert both with 3/4 race flatheads and manual am radios.
My Spica TC-50 were sold to a good friend, I gave him a Yamaha receiver and an NAD cd player. I suggested he buy a subwoofer to put with it, he bought a REL and immediatly I prefered the sound to my, then, new Thiel 2.2 Haven't seen him in years.
Selling my Porsche 911 Targa. Bought it new and sold it 5 years later. Best car I ever owned. Have always desired another. Alas with kids and all just not in the cards.