Well, you definitely need a pot so if you go with the Sound kit then you'll have to get it separately.
Palmer's How to Brew is available online (howtobrew.com), I suggest you read through that. I'm sure Sound is selling the updated version and it is well worth purchasing, but it is not absolutely required for your first batch.
I haven't gone through and figured out the rest of the differences, but the pot is really important. You can also buy it somewhere else.
I haven't been down to Sound, but I know the owner left Mountain to go start that place. Owners at both places are good guys. What neighborhood/town do you live/work in? There are several other places in and around Seattle.