Aside from its affordable price tag, the Z523 has a couple of strengths. For starters, the compact sub does deliver a good amount of bass and we liked how you can adjust the bass levels with the knob on the right speaker (there's a volume control knob above it). On music, the Z523 delivers ample low-end, and explosions in games and movies certainly pack some punch.
We also liked the connectivity options. Hard-wired into the back of the right speaker is a 3.5mm cord for connecting to your computer (or you could link directly to the headphone jack on your phone or music player). On top of that, you also get a headphone jack on the side of the right speaker and a 3.5mm audio input for hooking up other devices, such as an MP3 or DVD player. Finally, the sub has a set of RCA audio inputs for connecting additional devices, which could include a gaming system or a small TV (You could, for instance, run a PS3 to an HDTV via HDMI, then run composite audio cables from the TV's analog outputs to the Z523's composite inputs).
In terms of shortcomings, the Z523 just doesn't offer all that much in the way of detail (i.e., clarity). In other words, this little system sounds good for the money--and delivers ample bass--but don't expect high-end acoustics.
All in all, if you're looking for an affordable PC speaker system--and don't mind having to deal with placing a subwoofer on the floor--the Z523 makes for a good choice and is one of the better speaker systems in its price class (Altec Lansing's Expressionist Plus would be a close competitor). In case you're comparing it to the lower-priced Z320, this model offers significantly more oomph, but that's to be expected from a 2.1 system that features a separate subwoofer.