I have a very slow laggy xendesktop setup

after looking though everything i have come to the conclusion its a graphics adapter problem
when i looked at the VM ( these are hosted on xensever 5.5 based on Dell R710 server with 36GB Ram) it has 3 graphics cards installed one Cirtix one , One System center configuration Manager ( thats normal) and one Cirrus logic one which appers to be the one its using.

Any suggestions on why this is slow , an example scroll down a web page and it takes upto 2 mins and redraws the screen very slowly indeed.

thanks