Here is the 590 thread it's a good read... http://firewoodhoardersclub.com/forums/threads/new-cs590-timber-wolf-is-in-review.6077/
I like my CS-400 Echo, it's a fine saw. But one word of advice, when you buy it, the VERY first thjing you should do is remove the chain that comes with it, and drop it into the recycling bin since it's metal. then go out to your nearest dealer, and buy a REAL chain! The chains that come on them are terrible. I did that from some advice I got on here, and man was I happy afterwards, what a difference. I replaced mine with a Stihl chain, and it was like night and day. Good luck!
I bought the CS 680 and so far it seems like a nice saw. I may do a couple minor things to it at Pallet Pete's direction to help it breathe a little better.
I've always thought Stihl makes a great chain.. Echo makes good quality power tools that offer good value as well..
This may not have anything to do with why you asked but.... When I started looking for my first saw I kept reading that service and repair down the road was something to consider. Around me Stihl was the only answer. Lots of Stihl dealers close by but only one Echo dealer and a couple of Husqvarna dealers that were more then 15 miles away. Now if I was comfortable wrenching on them that would not have played into my decision as much as it did.