Well, I am riding the same boat here. In fact my boat is still docked. I am still collecting parts and yet to assemble the pc. A noob really but I think I am entitled to share my opinion too(however noobish it may be)
Assuming this is your first attempt at making a higher end pc you have not made a mistake imo.
Yes new cards are out, yes they are great(despite the fact many ppl are dissatisfied & labelling them as flops) but my point is that every new piece of sophisticated tech usually has problems( which r ironed out eventually off course) . For tech savvy geniuses (like on this forum) these problems are not much of a deal but for people like us(again assuming you are new at this) these issues can be really over whelming. I chose evga 780 classified over 290x stock n gigabyte(both were in my budget) for reliability & after sale service of evga.(as per feedbacks on forums)
Now I also understand I might not be able to handle the 780 as well but I am not afraid as there are literally hundreds of threads about almost all the 780 related problems on the web. But I don't have guts to try that with newer cards. Also, with NVIDIA's new cards out, AMD should not be far behind with their newer offerings so ppl will say wait for them. So, I'd suggest you to just chill n rock your 780. Whenever you are comfortable enough you can add another 780 to the mix. 700 series cards are being discontinued so expect quicker price fall & discounts for them.