Steve, from the 225/75-16 you have on there now, the difference would be less than .5 MPH at 60 MPH. From a stock size, you'll be off ~2 MPH @ 60. You're speedo will be reading faster than you are actually going, which will help keep you out of trouble with "The Man".
Even if you can't find the Kumho, there's several other good tires available in that size, including the 2 you referenced above. I know I was very happy with my LTX M/S's that I had about 10 years ago.
As for the A/V stuff, I like to dabble a bit.....I haven't gotten into most of the really current tech lately such as streaming from a PC to multiple TV's or anything, but I spend so little time at home its just not worth it at the moment. I've got my nice home theater setup with a 50" plasma, HD DirecTV DVR box and Polk surround system, and I wind up watching most of my movies and TV from my 15" laptop screen and headphones while on planes or in my hotel room....:angry:
Although, I guess if I didn't, I couldn't pay for the other stuff.