I have two dual core desktops, and one Netbook. I find that the desktops with 4 gigs of memory on each, there is no problem to use KDE. KDE uses quite a bit of resources, so much so that on my netbook with 1 gig of memory When I play freecell, The cards jitter across the screen, indicating a resource shortage. The Netbook has a dual core atom processor.
On the desktop, I use KDE for a while, but eventually I get tired and revert to G6 and I revert back. It is not supposed to be that way, but it is. If KDE had lower overhead, it would be outstanding.
G6 on the Netbook works fine, with good response time.