In addition to str8's, I've been sharpening knives for the better part of 30 years. I have some old Norton oil stones that are about 12 x 2.5 or so..I have the entire Naniwa line.
Many times, I'll go from the 10k to 12k, then onto the Shapton 16k. It gives me great edges, and awesome shaves. If money was an issue, I'd skip the 12k, and go to pastes.
If you can afford it, I think it does provide some benefit. I really like the edge I get off my Naniwa 12k by itself too.