The 10ufd 25V are cathode bypass caps. Negative side of the cap goes to ground. Same is true for the 8ufd 450V caps, neg to ground. The 8ufd caps are decoupling caps. You can use any cap that is close to those values. For the 8ufd caps you can use anything, 10-20ufd. Same is true for the cathode bypass caps, 10-25ufd.
Fred
Yea, what he said! ! ! ! ! ! ! ! ! !
(Hey, Phred, we agree again on something! ! )
Without the decoupling caps you could easily get "motorboating", oscillations,or other anomallys in the audio. They are VERY important to have in there. However the value is not real critical as long as they are there.