The 598ci SI Combo does not have the 3 preset buttons, only 1 card slot, and is not Ethernet expandable..

Like Duncan said in his first statement..the 598 is a "limited down" version of the 798...

It is HB way of making SI affordable for more people interested in getting into the SI technology...

Other than the 3 items I listed above, the 598ci SI Combo and the 798ci SI Combo are exactly the same...

Rickie