While I have not heard the C370, I recently bought the C350. Nice sound for the money, but not good enough for me. I had already tried a more expensive ss integrated amp and that didn't cut it either. Since I had already sold my preamp (this was a downsizing exercise), I figured I would use the preamp section of the NAD for awhile. Not wanting to spend a lot because I do not listen to this particular system much, I bought one of those 80 watt AMC tube amps you see auctioned here and on ebay. I got a significant improvement in the sound. Bass was a little deeper, but not as tight. However, the midrange of the AMC is in another league compared to the NAD and just about any other ss amp I have heard under $2k. The AMC does not have as soft a high end as some other all tube amps (it is a hybrid design) so it may not work for you, but I think it is an excellent value and worth investigating. A tube preamp may also help you, but I am not sure what will yield the most bang for the buck.
