You have asked more than a mouthful for sure. I'll give you some of my opinions, but that's what they are, opinions. (Most questions you've asked can be answered yes or no and both could be right, depending on the individual)
- Is surround sound for everyone, or is stereo fine for many folks?
Surround sound is not for everyone.
This really depends on what the person in question intends to use their system for. If they want to use their set-up for music only then two speakers may be fine. In fact that vast majority of music is recorded for playback on a two-channel system. For movies and television though surround sound really is like having a bit of the movie theatre in your house with you. Also new audio formats have arisen that have been mastered specifically for multi speaker playback. These new formats are called SACD and DVD Audio. Also many concerts have been put on DVD, can be played back in 5.1 surround sound, and sound fantastic. A person must also be comfortable with newer technology to delve into today’s equipment. Take a look at the back of a receiver in 1970, and then take a look at the back of a mid priced receiver today. Yikes, what a difference!
- Aside from surround sound, are there other advantages to newer equipment – i.e., Is the sound quality better?
Again this depends on the listener. There are people who will swear that the sound from a 1970’s stereo receiver can’t be beat by anything on the market today. Then there are those who’d say that the “warmth” those old junk boxes instilled in recordings is nothing but distortion that today’s digital connections allow you to get rid of. Anyone being honest about the difference in sounds will tell you that it is a matter of whose ears are hearing what. New receivers do more work than old ones, for example video switching and up converting. One interesting new development is the use of HDMI. This is a new way of transferring audio and video via one cable. This technology isn’t all the way there
yet but it's heading that way. Basically the newer receivers are better at multi tasking, but that may be a moot point for the guy who just wants to rock out with his stereo an hour or so a day.
- Do amps and speakers “wear out,” or can they perform well indefinitely, with proper care? Are some types of equipment “safer” to buy used than others?
Amps and speakers do wear out. Basically like everyone said you do get what you pay for. Initial quality tends to translate into lasting quality. Stand alone amplifiers (meaning just a power amp, no processors on board) do tend to have a very long life, people often say things like, "I've had my Marantz amp for 25 years, and it's still kicking." Amps don't become outdated the way alot of other equipment does. Older speakers were often made utilizing foam around the drivers. Foam does rot, so often times drivers in older speakers have to be replaced. This can be every ten years or every thirty years, depending on alot of variables. Some technology isn't really out of date, even by today's standards. A good AM/FM receiver from 20 years ago is still a good stereo receiver today, actually probably better than most of the ones out on the market today in my opinion. Sure you may have to get up to change the station, but the sound is still on par with today’s stuff. Don't forget though, now satellite radio is looming in the background. When looking at used equipment research is very important. Just do a google search for the product and then hit some sites like this one to ask for opinions or go to review sites like audioreview.com. Certain brand names have earned reputations over time. Names like Marantz or McIntosh or many others usually mean quality, but not always. Look for reviews. If the thing was a lemon 20 years ago, it's still a lemon today, someone will have written a review and posted it on the web.
- What types of audio systems are mature and good bets to buy now? Which ones aren’t? (For example, are 7.1 systems perfected, and offered at good prices?)
Audio systems are pretty mature up to 7.1 speakers. You do need more room to run seven speakers than you do five though. You can't just wedge two more speakers in there. One thing to note is that there are no discreet 7.1 formats. What this means is that no movie or music format is designed to put out sound to seven separate speakers. There are discreet 6.1 DVDs out there tough, and they are IMO the best sounding movies out there for watching at home. There is a discreet 7.1 format in the making, but when it gets released is anyone’s guess, and today's receivers don't have a processor to decode it anyway. Watch out for 9.1, it's on the way supposedly. All of that being said 7.1 matrixing is the best sound for a big room IMO. Other audio trends to be wary of are the aforementioned DVD Audio and SACD. They were supposed to have changed the way we all listened to music by now, instead they are fighting to stay alive and have become a niche market. Also you may want to point out in your article that two new DVD formats are about to emerge. They are called HDDVD and Blueray. Both of them plan on using discs that can hold over 30 gigs of data compared to the 4 gigabyte dvds we use today. All that that extra space will allow is too lengthy for me to get into. It's too early to tell if these new formats will be successful or not.
- Are certain times of the year better than others for getting bargains?
Times to shop include just before or after Christmas, or whenever model years change (usually at the end of the year as well). If you can live with last year's receiver as opposed to the brand new model you can save a bundle generally speaking. For example the receiver I have on order cost $1300 last year, but I purchased it for well under $500. That bargain may be rare, but it is not unique. Many manufacturers are also using online retailers to sell their products now and that provides additional savings (JR.com seems to be a good site, lots of quality manufacturers and decent pricing). Check manufacturer's websites to confirm that you are using authorized retailers though, as you may not get a warranty otherwise.
