As the posters above have pointed out, ARC has had a long and distinguished history of making audio equipment. Some of their equipment has received more acclaim than others, but there is little doubt that the company was way ahead of it's time in the 1970s. The SP-3A1, the D-76A, D-150, and the D-79 were and still are excellent pieces of equipment. This is not to say that if you have an unlimited budget you can't get better sounding equipment 30 years later (ARC would certainly say you can), but dollar for dollar in 2005 dollars, each of these pieces of equipment (when you can find them in well cared for condition) will sound as good as or probably better than just about anything you can find for a similar price regardless of manufacturer or when it was made. Setting aside how they sound, if you buy one of these 1970s models for fair market value on Agon you will have a strong investment that will hold its value. For example, if you could find a SP3A1 in 7 condition on Agon for $1000 or so you could buy it and listen to it for a year and then probably sell it for the same price. How many other pieces of equipment can you say that about? Not many, and probably no preamp that could buy for $1000 would sound any better than a SP-3A1, except possiblly an Audio Research SP-8 (which happens to be a 1980s model and will probably cost a bit more than a SP-3A1). You can debate which will sound better a SP-3, 8, or 10 (well, ok the 10 wins, but it's $2.2k) or which is a better value, but whichever model you buy based on synergy with your system and your budget, you will have a highly enjoyable listening experience and you will get your money out within a few weeks of the time you list it on Agon.
Finally, as the posters have noted, service doesn't get any more friendly or helpful than it is at ARC. And this is important because to be square, anything 30 years old could need some parts or service (and that's true whether it's solid state or tubes.) In fact, it's probably hard to come up with many (any?) other pieces of equipment from the 1970s that would be as easy to get serviced. The list would probably be zero if you want to have the service done by the manufacturer. ARC just stands out a cut above when it comes to both sound and service.
Is ARC equipment worth it? Absolutely. - And this has been true across 3 plus decades.
