Sluggish ui on a fresh ubuntu install

Hello!
Once again my lack of know-how in the linux world has brought me back here, where the infinite knowledge lies :D. I have just installed ubuntu on my server which is an HP dl380 g5. I know it's aging. And based upon what I have been reading, is that it may be too slow to handle Unity. But before I go ahead and install another, light weight distribution, I would like to make sure. I am still pretty new to Linux as a whole, but I do love ubuntu, mainly because it's what I have been using this whole time.

How do I make sure its not something else besides Unity?

My specs are 1 single (it can hold two) Intel xeon E5440 @2.83 with 8gigs of ram.

This Server is not intended for running a 3D accelerated graphical user interface. As far as I know this server has an ATI ES1000 graphics chip which is not supported for 3D acceleration therefore Unity is falling back to llvm-pipe rendering (3D OpenGL crunched by the CPU). Use a 2D desktop like xfce ore lxde if totally necessary but I would recommend using no GUI at all for a server.

Thanks! I just started using xfce. Much smoother