NVDucati -- Your math looks correct to me. I just never trust the actual specs from, well...just about anyone. There's a reason they recommend 2A / 25W, and I don't know that I would even trust those numbers. But I'm a major skeptic; would probably work just fine.
I have the same setup as you in the front: BlinkerGenie for indicator lamps as both turn signals and running lights. Around these parts, amber rear running lights are illegal (but, oddly to my mind, amber rear brake lights on a motorcycle are ok).
blaustrom -- Since most aux lights don't have tight beams or a proper cutoff, they require dimming, anyway, so as to not blast oncoming drivers' retinas into oblivion. PWM dimmers are cheap and ubiquitous. I like the ones Diode Dynamics with built-in bypass
(though I got mine before they doubled the price).
For my setup, I have aux / conspicuity lights dimmed with lowbeams, and full power with highbeams. I dim them enough to not blast oncoming traffic's retinas and to ensure my turn signals are visible. (Note I don't use the dimmers noted above for this, the dimmers are left over from a prior, failed project.)
drrod -- Just because one can, doesn't mean one should.