If you ever work from home like many people do these days, and you like listening to music while you work, there are a lot of different ways to go about having music play in your work area without using headphones. While there are quite a number of various cutesy speaker options out there, I personally don't like them because you will end-up with something that is junk that you will need to replace in a couple of years because of how quickly technology changes, or because of a component failure.
Another great area for a system like this would be a work area such as a garage or shop. Why spend a bunch of money on a stereo that doesn't get a lot of use or is exposed to elements like oil, grease, etc. I can attest after spending a good part of my early 20's wrenching on cars and motorcycles, a cheap stereo in your garage is a great investment.
When I build audio systems, I like to combine a bit of old-school and new-school technology to get the best of both worlds. As far as old-school goes, I like to make sure that each component of an audio system is replaceable to account for failure rates and technology advancements. What does that mean? In simple terms, I like to make sure each component of a system is separate. For example, I'm not someone who would buy a coffee machine that also grinds coffee beans. Once the grinder goes, the coffee machine is likely worthless. Instead I own a bean grinder and a coffee machine which are separate.
As far as new-school tech goes, I hate wires and unnecessary complications. One of my favorite somewhat recent technologies that I've been using a lot of is Bluetooth. Luckily Bluetooth pairing is a pretty pervasive technology by now, so not only is it built into most things now, it's also easy to find all kinds of inexpensive things that speak Bluetooth.
One other interesting technology that has been becoming more and more popular are MOSFET Class D amplifiers. The majority of these amplifiers are definitely NOT audiophile grade at this point, but they are compact, can put out a lot of power in a small space, and don't get nearly as warm as some of the more classic MOSFET amplifiers. Some places where Class D amplifiers are currently used are in the "home theater in a box" type systems, low-end car audio amplifiers, and smart phones.
What I Built
With all of these things in mind, I set out to build an inexpensive audio system for my office, and here is what I came-up with:
Total I have invested: ~$160
Most of the cost is actually from the bookshelf speakers, which I'm reusing from an older surround sound system I built about 12 years ago, so I'm not even sure whether I should consider the cost of them or not.
Overall, for the small amount of money invested in this system, it works very well. I put this system together in April of 2013 and here it is seven months later and this system is still working great. Even as cheap as these components are, I have yet to have a failure or major issue.
I have the system paired to a couple of MacBook Pro's (one for work, one for home), and my phone, so I can play music from whatever device I want to. I'd assume this amplifier is probably only putting out about 10 watts x 2 channels RMS, but it's still plenty of power for my small office. I haven't really tried to push the speakers or the amp so I'm honestly not sure where it would begin to distort or sound terrible. These little amps only have a sound-to-noise ratio of about 80 Db which is not very good.
Since I originally set up this system, the market has exploded with all kinds of amplifier options. Although the power is plenty for me, I'd consider picking up a more expensive amplifier which is much better quality. If you spend say $70 instead of $20 on the amplifier, you could get an Amphony 200 which has much, much better specs and power. I do think if I were wanting sound in a larger area such as a garage, I would probably opt for a more powerful/expensive option.
I would also love to have a subwoofer, so I'd have to take a serious look at either adding a powered subwoofer, or maybe one of the 3 channel amps which also have a mono output channel for a subwoofer. I'm still thinking about this issue because you need to be able to control the level of sound from both the bookshelf speakers and the sub from the same volume control.
Lastly, I think it would make sense to maybe use a small piece of painted MDF to fasten down the amp and bluetooth receiver just to clean up the installation a bit. I didn't take any photos of my setup because it doesn't look very good in its current state.
As you can see by the price I spent on the components (minus the speakers), this is a very inexpensive system to configure. Since the time of writing there have been quite a few more Class D amps put on the market, so I would research some of these amps and see if it's worth it to spend a bit more on one.
I'm very satisfied with this setup, and I hope it gives you some ideas about how to setup your own inexpensive audio system.