Has technology evolved? Definitely. Is there a "huge" difference in sound...that's a very difficult question, that each person has to hear for themselves. I did an audition, and the difference wasn't huge in any context of the word, at least to my ears.
I've owned the N805 and 805 Signatures, and did a lengthy audition in a well-treated and equipped room between the 805 D2 and 805 D3. Did the D3 sound different - yes it did. But the difference was not "huge", to my ears and my perception. There's another thread here about these speakers and I'll post here what I posted there on the same topic - my immediate reaction, after hearing the D2 and D3 side by side, was that I imagined buyers might use the D3 introduction as an opportunity to pick up D2 models on sale. They were close enough that the D3 introduction seemed to me to be a great chance to get D2 on clearance. If I was going to make a purchase that day, that's how I'd have gone. Interestingly, out of the three of us (Magnolia rep, myself, my wife), both the rep and I preferred the D2 and my wife the D3 so she was outnumbered :-)
Short story long, I like Jafant's post before me - 805s on the cheap seems a great move. They were fantastic when they were introduced, and still are today - all the technology in the D3 doesn't minimize how good the originals were and still are.