That depends.
Whatever the case, having the xku LNB is not going to be advantageous for you because that LNB is for receiving signals from the newer satellite Anik G1 (in addition to the older satellites Anik F1R and Anki F2). Florida is outside the footprint for Anik G1, so even if you do have the xku LNB you will not be able to see any of the channels that come from that satellite. So if you currently have a working system you will be wasting your money to swap out the older LNB for an xku.
So to answer your question, whether you need it or not depends on how your receiver is currently set up. If the channel map in the receiver has been set up to utilize the xku LNB, then you cannot use the older quad LNB with that receiver (and vice-versa). If that is the case, then you have two options:
(1) contact Shaw and have them change the channel map in your receiver to work with the older quad LNB. Calling Shaw from outside Canada may raise questions about where your receiver is located, though.
or
(2) purchase the xku LNB and install it on your 75E dish with the understanding that you will receive all channels in your package that come from Anik F1R and Anik F2. Channels in your package coming from G1 you will not see. Be sure to purchase the xku LNB that is for the 75E, as the LNB for the 60E will not work well with a 75E dish.