Bought my 5As for under $6k and they are an excellent speaker. Hard to find something in that price range that will be much better. I build my own components so I can't help you there. I was really impressed by the model 7s and if I was going to spend that kind of money that is where I would look for my next speaker. Not sure how much improvement you get from the 5As to the 5Cs and it depends on the used prices.
Happy Listening.
Happy Listening.