I think he is trying to sell you one size up from what you really can use.
The Prizm Deluxe is a new model of the classic Prizm (still only a few years old). Its rated for 100gal aquariums and smaller. Petwarehouse.com has them onsale for $79.99
The Prizm Deluxe PRO is somehow different in that its rated for up to 300 gal
aquariums. Its also onsale for $159.99
Im not sure but i think both now include a surface skimmer attachment.
I think both of the models listed above are different than the old 'classic' prizm that I and many others have. They classic prizms had people complaining about them being loud. I did not think mine was overly loud when you figure 90% of the noise is caused by the air being injected into the water at the impeller.