I've been using a combination of a Bracketron satellite radio dash mount (just the portion that attaches inside the dash) and a Bracketron Universal GPS Window Mount (just the portion that holds the iPhone) since 2009. I got both parts at Best Buy. They installed it and only charged me for one of the two. You can glance over and easily see what's on the screen.
The proclip USA is a nice setup. I have that in my car. It was a little spendy, but I like it alot uses the 30 pin to lightning adapter. FWIW, I bought the adjustable one for a small case iphone 5 which is what I was using it with originally and it still fits the 6 with a small case. A little wobble if you keep it loose, but not enough that I'm concerned about it.
I am another ProClip user. I have used them in all my cars for the past 8 years or so. You buy a mount specific for your car and a holder specific for your phone. As noted above, it is a little pricey but well worth the money in my book. I actually do not buy the holder for my phone but buy one of their adjustable ones. That allows me to make it work with or without a case. I am using the same one on my 6+ as I did on my 5 with no issues whatsoever. I just expanded it's grip width and voila. I use the apple leather case on my 6+ and it fits like a glove in the proclip.
I'm still using using my proclip 5S rugged case size mount which fit my life proof with a 6 using a speck candy the only thing is the thickness is too big but not bad for now until the proper stuff is made