I use my Naniwa Sink Bridge all the time and love it. It's a good accessory. http://www.chefknivestogo.com/nasibr.html
The DMT XXC is also something I use almost every time I sharpen. I usually do a quick flattening on them right before I begin. We have some other ones but I like these the best. http://www.chefknivestogo.com/dmtextracoarse.html
You can use the DMT plate for very fast metal removal but I usually find the Beston 500 plenty fast and a little easier to use for most steels. If you have lagre chips or tip repairs to do you can use the xxc.
Horse Leather and Rock Hard Felt Pad Strops are not necessary, especially when you first start sharpening. That said, I always strop my knives as a final step and I use my strops for quick touch ups between sharpening.
If you're looking for a good santoku that isn't too much money I really like the Sakai Takayuki hammered damascus. It's a good knife and will be fun and easy to sharpen.http://www.chefknivestogo.com/satadahasa18.html