I have a 2008 Toyota RAV4 with a factory connection built inside the center console to allow devices such as an MP3 player to be played through the car's sound system. However, when I would connect my wife's Sandisk MP3 player we just weren't getting enough volume output to hear music comfortably when rolling down the road at 70mph even with all the volume controls set a their maximum. Hence I purchased a Boostaroo Revolution R234-MC. Here are the pros and cons:

PROS: Very easy to install, just plugs in. Compact in size. Two output jacks for mulitple listeners. My Toyota also has a 12V power supply built inside the console, so power access was no problem at all. Also, with this power connection I don't have to worry about batteries needing to be replaced or recharged in the Boostaroo. Boostaroo claims an up to 4X increase in volume which is probably true. I was able to measure it against a known song that had been boosted by 10db (3X) and the Boostaroo was just slightly louder (I would guess maybe a boost by up to 12db which puts them into the 4X range). Within my car I did not notice any discernable hiss, amplifier interjected noise, or modification to a song's tone or frequencies. I did not try headphones as I bought the product to go through my car's sound system and I won't wear headphones or ear buds when I'm driving. So, the product did what it said it would do and I now have MP3 generated songs playing at an acceptable volume level in my car.

CONS: Just a little pricey I thought, but I'm willing to pay a premium if the product is reliable and does the job and does it well. Which the Boostaroo does for the purpose I bought it for. The one "feature" it has that I don't like is their cross channel circuitry (read - digital reverb). It adds a touch of reverb to every song played through it. To the casual user, you probably won't notice it much if at all, but to the audiophile you'll pick up on it right away. I don't like that the device is adding something to the music that wasn't there originally. I wish it wasn't there at all or at least give me the capability to shut it off or bypass it. Boostaroo should be more open about telling people about this feature. The refer to it in their literature as "enhanced audio", nah........... its digital reverb so lets be forthright.

SUMMARY: I really like the product. If it didn't add that hint of reverb I would have given it a 5 star rating in all categories. My recommendation to them would be to drop the reverb - period, or at least give me some capability to bypass it. I would recommend the product to my friends with the caveat about the digital reverb.