Just to add to my previous post, while rectangular shapes are generally easier to measure for volume and to construct for rigidity, the shape can have disadvantages in managing soundwaves coming out the rear of the cone speaker and into the box. They can bounce off corners and the measurements of the sides can introduce distortion (which is why they avoid perfect cube boxes, since that will amplify the distortion within a narrow range).
On to your speaker options - the cheapest many people recommend are the
Dayton B652 but they'll still need an amplifier (and a DAC if you're planning to use it with a computer and not its soundcard).
Personally for a computer I'd rather use an active monitor and either a DAC (which is an audiophile terminology for the equipment) or an interface (which is a pro-version, probably has an ADC as well as a DAC), which puts the volume control within reach (and possibly much better SQ than an ordinary soundcard integrated into a motherboard), plus these are nearfield monitors. All measured performance/specs are from the microphone at the same distance as you would if you were on a desk, instead of what hi-fi speaker manufacturers assume will be you sitting at least 1.5m or more from the midpoint between two speakers about 1m or more apart. They also come with dual amps in each monitor designed specifically for the tweeter and woofer. My long-running favorites for not a lot of money are the
Samson Resolv R5a and
KRK Rokit 5; not sure what others are out there though. Think of the Audioengine A5 as a speaker that incorporates the basic design template but designed for a home listening setting instead of a drab grey studio (thus the colors, the target market - music lovers and not pros, only mini-TRS and RCA, now with USB Port for charging, etc). The A2 would be more like Samson's MediaOne series.
