Spark Booster is such a versatile, thought out and magnificent sounding pedal, it's a no-brainer at this price point to have at least one in hand. This will work as a clean booster, mid boost or bass heavy boost with a dip of a single mini switch, giving you separate volume level and gain controls, and also adding up bass and treble EQ in the mix. Very quiet operation with no extra hisses in your signal.
Use it in the end of your chain for firing up your preamp, put it in the beginning for overall tonal shaping, or even use it as a light gain overdrive -it performs excellently in all of the above. At the monent I use Spark as a tone shaper for my Fulltone OCD running with 18V, and it works wonders for the sound, seconding as a light overdrive when necessary.
The build quality is excellent; I have only one minor issue, that being a LED light that seems a bit loose. However, I doubt it will cause any problems since it's in an area that probably won't get any hits or bumps. Other than that, the case is solid, the knobs are firm, the switch robust and the jacks well placed and connected. As a bonus, the casing is easy to open with only one large sturdy screw.
All this, and it's dirt cheap for the quality. My very heavy recommendation. It's so good I will need another for home use, and probably a spare one for the gig rig in case the main Spark craps out on me in an inconvenient hour. (I don't expect that to happen, however...)