Available now for $99, the S4A headphones come with a unique accessory we don't normally see packaged with headphones: software.
Although not necessary for audio purposes, the Klipsch Control Android app lets you change the functions of the remote buttons--you can specify voice search and commands, auto-dial a phone number, and advance tracks. Also unique to this model is a separate mute button.
In terms of specs, the S4A have the same guts at the original S4s. Each earpiece uses dual-magnet microspeakers with a frequency response range of 10Hz to 19KHz, so we'll expect the same noise-isolation and boomy bass that we love about the S4.