As George stated, you can replace the silver mica's with .1uF Sonicap's if you want. I found that in doing so resulted in very annoying artifacts, so I removed them. The idea behind using bypass caps is to achieve a better sound when used with cheap electrolytic caps like Polk uses. When upgrading to high end caps there is really no need for the bypass caps.
Note: If you choose to not use the bypass caps, you will have to use a jumper for the one located closest to C5. I did this by dropping the top lead for C5 from the P3 hole to the actual top hole for C5, then adding a jumper from R2 to P3, thus completing the circuit. For the silver mica located closest to P1, a jumper is not needed.