Ok, started looking into this for no particular reason. The kit says it uses a (National Semiconductor) LM3916. So I looked up that part. It turns out you can run this to have a bar display or a dot display (dot display being like the Lunatec V3). The kit says that you can choose between bar and dot. If you run it as dot (pin 9 on the LM3916 left unconnected), you will not only have a display that mimics the cool V3 display, you will save quite a bit on power. Each LED will probably be drawing 20-30mA of juice, so limiting to 2 LEDs at a time (dot mode) will give you much better battery life than running it in bar mode (probably talking about about 200ma vs 40mA in dot mode).
The LM3916 spec sheet also discusses how you can limit the current draw of the LEDs, which will make them dimmer, but will also further extend your battery life. Motivated folks who want to go this route should get the disassembled kit and read through the 3916 spec sheet on this topic. By substituting a couple resistors in the kit, you'll be able to save a bunch more power. You could probably also look around for low power LEDs. The 3916 and other components don't draw much power. If you change this to dot mode, reduce the current delivered to the LEDs, and/or change out the LEDs for low power versions, you could put together this VU meter so that it draws very little power.
Also, Matt, the kit says it has a low input mode vs. a high input mode. Difference seems to be a 47k resistor vs. a 470k resistor. Maybe you can solve your problem with too little LED action by changing from high input mode to low input mode. Maybe a jumper selection or maybe have to change out a resistor (R7?)