Anyway, after much googling, and only catching one-off comments regarding this... As I suspected, most car chargers/usb chargers simply can't keep up with the phone while in use.
The issue is due to the amount of Amps the charger puts out. My current charger, meant for an iPod, only outputs 500 mAh or .5 A (Amps). The wall charger that came with the phone puts out .7 A. (I'm assuming the wall charger would keep up with all the goodies turned on.)
I wasn't able to discern the output of the official Samsung car charger. However, I did find a charger that puts out more than .5 A... Significantly more. For like six bucks...
The Motorola rapid rate vehicle charger seems to fit the bill. I imagine .95 mAh will do the job nicely. From what I understand, it is compatible with many phones, and only outputs what the phone "requests".http://www.amazon.com/gp/product/B000S5Q9CA
I've yet to receive it, and it's hideous. (Who really needs a coiled cord for anything, ever? Other than stressing the charging port and being overall unwieldy.) I plan to use my current charger unless I'm in a fix, and keep this one hidden away. I'll post again if I find anything significantly negative about the charger.