The ICOM SP-23 (SPK-08), Yaesu SP-8 (SPK-04) and JRC NVA-319 (SPK-6DS) are intended to cosmetically match ICOM, Yaesu and JRC receivers and transceivers. Acoustically, their performance is nearly identical. They both work on any receiver with an external speaker jack, and have push-switch settings to reduce either high (treble) or low (bass) sound in order to reduce shrill interference or emphasize voice tone. 

    The SPECO DMS-3P (SPK-03) allows the full audio tonal range of your receiver to be heard for both speech and music; it is essentially a "hi-fi" bookshelf speaker in a sturdy, metal cabinet, and packs a wallop for its size.

     The VALOR VS-6 (SPK-07) is a compact, quality speaker for mobile applications; it has a treble-cut switch to help reduce impulse noise interference from car engines as well as annoying background hiss on a receiver or scanner. 

    The GAP "Hear It" DSP(SPK-05) is an active filter; that is, it isn't just capacitors and resistors, it has electronic components like ICs and transistors. It is used to cut off high and low frequencies much more accurately than simple tone controls. Therefore, I'd put it with the external speakers that have tone controls.