Nice impressions.
If you spent more time with the 595's and the 650's you will realize that the 595's have a more "forward" and "bright" sound. This means they have more emphasis on the highs than the 650's do. The 650's and 600's are a bit laid back.
Having been in the hobby for a while...the 595's can have a "honky" or "bloated" mid/upper range. This means its a little too emphasized and not as well defined. They are still excellent headphones. I was happy with them for a long long time. The 650's just excel at being much more refined - that is something you're only going to get more of if you invest in a good amp/source setup.
So, stay with the 595's and really get to know the sound signature, you'll enjoy them even more.
Congrats on the purchase!
