arkodeon, no offense (and you're entitled to your opinion of course), but as to this:
And you forget, the Death Star is not a rehash of the LAAT, as they use completely different energy sources; the Death Star's being the most rare, and could only be found on Mygeeto, and the beams, while potentially the same, require different workings of technology. The LAAT came out of a single shoot/barrel-like expeller, while the Death Star's laser came out of a dish, and was composed of smaller laser beams.
I don't know what EU retcons you're reading or where you're getting that, but I'm talking about a direct comparison from the movies. Blaster shots for the most part are red "bolts" (though green is more common for starship level weaponry, used by the Empire). The Death Star has a bunch of smaller green BEAMS that form into one larger green beam that fires in and causes massive destruction. It looks more like a Star Trek phaser than the typical "energy bullets" of Star Wars. Look at the LAAT ball turrets. They fire a series of smaller green beams that form into a larger green beam that sweeps in the destruction. Hmm... looks familiar! A similar technology is used on the Republic thanks (the ones with lots of tiny legs on the bottom). The guns fire a few smaller beams that form into a large blue beam. And even without an exact comparison of the pics, you can see the older weapons also employ a "dish" of sorts on the gun end.
The only difference I see here is one of scale. The Death Star does not represent a breakthrough in new weapons technology. It's merely a HUGE version of these early energy beam weapons. Sort of like how a cannon is based on the technology of a pistol, only much larger and much more powerful as a result. Sure, it is a new application of existing technology. They had energy beams mounted on Capital Ships as seen in ROTS during the battle over coruscant (powerful enough to shear another starship in half). They had large vessels, but the Death Stars are truly huge. So they had to keep the structural integrity even during FTL travel. Planetary shields they already had as well (at least contemporary with the first Death Star, if not before, per movie evidence), which is just a larger application of theater shield technology (which even the Gungans, a supposedly "primitive" culture had access to).
Also, remember that according to AOTC, the Geonosians planned to build the Death Star, so it wasn't something the Empire came up with through some amazing new discovery.
The sun crusher is supposedly a bunch of new tech, but it was created in the EU and suggested to have been built during the time of the Empire and was just never used and forgotten about. The World Devestaters use technology similar to construction droids just on a much larger scale (both EU inventions of course, but you see the pattern developing?).
Other than the Sun Crusher, really all this stuff is old stuff used in new ways, it's not a radical breakthrough.
Also, one last nitpick, there is no actual "year zero" in the BC/AD dating system. The years decrease until you get to AD 1 (the traditional date of Christ's birth) and then after that it increases. That is why the centuries before Christ are labelled with the number, while the ones after are one off (so we're in the 21st century AD now, when the year is in the 2000's, but the 21st century BC would have been 2100's).