I have the HPE-510y, and I have upgraded the GPU (nVidia GeoForce GTX 550ti) and PSU (Dynex 450w), and added a second HD (WD Caviar Black 320GB) shortly after purchase. A little over a year later, I have noticed that the inside of the case seemed quite hot, so I installed two fans that I placed over the holes on the side of the case to help with the cooling.
While my CPU (AMD Phenom II X6 1055t) has a "max" temp rating at around 62c and my GPU at around 70c, I wanted to do TWO things: Replace the case fan... and replace the heatsink on my CPU. Any advice in this matter would be greatly appreciated. :-)