My C6 has the 6 CD disc changer which I actually like. I did not really want to change it out or switch out to an aftermarket head unit but wanted GPS navigation. Don't really need navigation very often, but getting ready for a few hour ride to Carlise. I have used a Tom Tom but it was often hard to hear over music and the windshield mount seemed bulky and I use the windshield to mount the radar detector. Just started using this "Steelie Magnetic Vent Mount" (Cabelas or Amazon - $39.99). It is a reasonable size, not too bulky. It has a lever to securely attach it to the vent slant. You can easily pivot the phone to any angle to view the screen when driving. There is a strong magnet that you secure to the back of your phone. The phone easily detaches with a simple twist.
On the advice of my high tech son, I down loaded the WAZE app to my phone. After using the app for a week, it is spot on accurate for navigation and also shows traffic, construction, and speed traps.
The great feature of this app is you can connect your phone to the factory radio if you have the accessory input with a simple cable. You can then listen the music stored on your phone while using the WAZE app. The audio directions will reduce the music on the radio so you can easily hear them.
You can purchase more adhesive magnets so you can use other devices on the vent mount (I-Pod, another phone).
Only disadvantages I have found so far, the audio and power cables show which takes away from a cleaner appearance, and the volume of the music going from the phone to the radio is adequate but not as loud as when I have my I-pod connected to the accessory input. The WAZE app can drain the phone battery quickly so you need the power cord connected.

While not as clean as a new navigation head unit, I found this set up an efficient way to add GPS navigation while maintaining the factory radio/CD changer.

 

I think what you did is a good solution. Waze and your phone are going to be the most current. The main reason I replaced my head unit was to integrate cameras. One heads up though. If you lose cell phone coverage and then need to re-route, Waze is not going to be able to do it without your cell connection. This is where the built in maps of a Nav head unit can come in handy. However, there are also navigation apps for your phone that will allow you to download maps into memory as a backup.

 

I tried the vent clip style but did not like it. I was also afraid of breaking the vents from the weight of the phone. Here is what I chose. Picture is in my F150 but have it in the same location on my Vette. Wizgear two mount kit sells for $13.99 on Amazon. Score!

 

i dont like vent mount device, my pick will be proclip