Here's Crutchfield's response to upgrading the factory 14 spk Bose system:
I'll be happy to help with your question on upgrading the factory system in your Infiniti M45. Unfortunately, I'm afraid upgrading the factory speakers will not be a simple task. We do have speakers that will fit the front and rear doors with only minor modifications. You can see all the speakers that will fit with our "Outfit my car" feature:
http://www.crutchfield.com/whatfits
To install new speakers in the doors, you'll need to use the adapter brackets we furnish and drill new mounting holes in the doors to mount the brackets.
The center dash speaker is not a standard size speaker so replacing it will require custom installation and fabrication of a bracket to hold the new speaker in place. The same is true of the tweeters in the front doors.
The subwoofer in the rear deck is a 10-inch woofer. We have several 10-inch woofers that will fit, but the carpeted cardboard trunk linker will have to be cut out to gain enough depth. In addition, new screw holes will have to be drilled to mount the subwoofer. I don't have any power specifications on the factory sub amplifier, but I doubt if it is powerful enough to drive an aftermarket subwoofer. Factory amps almost never are. That means an aftermarket amplifier will be needed if the factory sub is replaced.
Unfortunately, the rear deck corner speakers and the speakers mounted on the front seat backs have not been researched so I don't know if those can be replaced or not.
Overall, replacing any of the speakers will require minor modifications at the very least, and custom installation with major modifications in most cases. Since we have no specifications on the factory amplifiers, I don't know if the new speakers will give you the performance you want with the factory system. In many cases, the components in complex factory audio systems such as this one are designed specifically to work together so replacing part of the components in the system will actually degrade the sound quality rather than improve it. Unless you want to have a professional installer replace the whole system, I really don't recommend replacing just some of the speakers.
If you want some extra punch in the system, you might consider adding an additional subwoofer to the system rather than replacing any of the factory components. One way to do this is with a powered sub such as the Infinity BassLink:
http://www.crutchfield.com/cgi...sslin
The BassLink doesn't take up a lot of cargo space and gives you plenty of bass. It has speaker level inputs so it can be added to a factory system. However, since your factory system probably has its own crossover points, I recommend using a processor such as the MTX Re-Q to add bass back into the system and improve the performance of an aftermarket sub:
http://www.crutchfield.com/cgi...36req
The BassLink does not include all the wiring necessary to hook it up. We recommend a 10-gauge kit such as this one:
http://www.crutchfield.com/cgi...2pa10
I know that isn't exactly the news you wanted to hear, but I hope that helps. When you're ready to make a purchase, just visit our web site at
http://www.crutchfield.com. Thanks again for your e-mail. Please let me know whenever you need anything else.
J