Mazda isn't worried about Honda. They are still primarily a niche auto maker, producing a modest but well thought out product line. They sell to a specific demographic that differs from buyers of Honda, Toyota, Nissan, etc. Their target is people who want the same types of cars, but that are more practical yet fun to drive. Hondas and Toyotas typically are boring, and their "legendary" reputation for quality is mostly fabricated. Mazdas have lasted just as well, or better, but don't get the same glory. Mazda also doesn't try to manufacturer such a reputation, instead relying on their cars to do the selling.
As for replacing the head unit, it's not nearly as scary as it first appears. Now that kits are available, and head units are designed for modern car electronics, it's really just a matter of putting it in.
I recommend the Pioneer AVIC Z120BT because it will fit, the ease of install, features, price, and owner reviews (for the Z110BT). It has a very nice NAV system with 12 million POIs, full Parrot bluetooth, iPod interface, backup camera input, voice command even for the iPod, customizable display screens and colors, and is ready for SAT and HD radio. It also has a Zone 2 output, so you can listen to radio, etc in front, and send another source to the rear passengers.You can even find places on your iPhone and transfer them to the head unit for mapping. It even has Eco Drive which goes way beyond the standard trip computer. Also, the NAV is stored in the unit, not on a disc or card. The NAV updates are also a lot cheaper than factory discs.
http://www.pioneerelectronics.com/P...eo/In-Dash/GPS-Navigation-Systems/AVIC-Z120BT
I also recommend buying it from Crutchfield. No, I do not have any stake in them, but they have always gone above and beyond other sellers by doing their homework and putting together comprehensive lists of components and parts need for each specific vehicle. When you buy a unit, they include the adapter frame, harness, and vehicle specific instructions.
http://signature.crutchfield.com/s_130AVIC120/Pioneer-AVIC-Z120BT.html?tp=27996