I have an old arduino Duemilanove (with a barrel plug).................... and, although i have soldering skills, I would rather not be applying solder on such an irreplaceable board.
Some of the fully brightened demos i run do some serious flickering, I figure the answer is more amperage.
Indeed the answer is more amperage. You can read through other forum topics, where this issue has been adressed already, e.g.:
As far as getting more amps not willing to solder. If you don't feel comfortable in soldering a barrel connector extension in your baseboard to fit an external PSU with more current capacity, I'm afraid you're gonna be out of options. Electrically, there is only one way to provide more power, and that is to attach an external power supply via the common 5V bus. If you try to beef up just with a PSU with more power plugged directly to your arduino or photon, and you crank up the brightness, you're gonna see smokes coming from the microcontroller pretty fast. I advise you to reconsider and take the better alternative.