I tried a lot of available LED tail/stop lamp replacements two years ago. There are definitely more options available now.
I chose the 1157-RLX3 Luxeon 3W lamp from superbrightleds. It is the only one I tried that is bright enough. It has no white light for the license plate but it lights the plate pretty well (if red) anyway.
The light output is a bit hard to compare from the specs. The Luxeon ones are rated in lumens and the rest are in mCd, and converting between these is not easy. The Luxeon is rated at 65/240 lumens, the one you refer to is confusing but seems to say 8000 mcd spread over 40 degrees: a rough conversion comes up with 3 lumens. If that refers to one of the 19 LEDs, then total lumens would be 57. There's no reference to the low/high brightness you get with a stop/tail "1157" type bulb for this one either. Assuming the 8000mcd brightness is rated for the stop function and that it refers to individual LEDs, the 1157-R19W6 is about as bright on "stop" as the 1157-RLX3 is on "tail". Note that a normal 1157 bulb is over 400 lumens on "stop".
My tail light may be visible in full sun, it's marginal though but I don't care about that. The stop lamp is frigging bright even in full sun - that I like. At night both are excellent.
For safety I suggest the Luxeon 3 watt (or 5 watt if available) single LED lamp unit. It gives a good bright brake light. I have a box of other LED units I don't think are safe - the stop lamp is barely visible in daylight.
Don't try a white LED for a red signal lens. The way LEDs make white light is not direct, the LED is actually invisible UV light and it excites a mix of phosphors that give a sorta-white light that has very little red light in it. For the tail/stop light go with a true red LED. For signals the white LED produces a decent amber but a true amber LED can be much brighter and more efficient.
I don't know how you came up with a 75% load reduction using LED lamps. The headlight is at least 35W, the rest of the lamps can't come close to that. The stop lamp and signals don't really count since they are rarely on. The 1034/1157 bulb "dim" filaments (tail and marker) are 8W, the instrument lights are maybe three watts all put together. That's 35% of the stock lighting power load taken for non-headlight use, 25% if you have a 55W headlight; plus the LEDs do take some power too.