Good idea Phil..

Just to make sure I understand Aksa 100 Valhalla correctly.
Anyone replacing aksa100/n with BG caps:
C11, C3 and C13 must be 100v version. C4 can be 50v.
Can replace C7 and C2 with BG NX 6.3v caps
However, I don't quite understand C10 and C12.
C10 and C12 are rail caps, and should be rated to around 20% more than applied voltage. On the 55W AKSA, this means they can be 50VW, but on the 100W AKSA, with its 50V rails, they should be 63VW. Since Black Gate, Bless Their Socks, don't make a 63VW (now that's a smart commercial move!) you are forced to use their 100VW cap, which is MUCH more expensive, around $US6.95 on special at Parts Connexion. across it and can also benefit from the NX series.
On aksa100 C10 is 100nf 160v cap and C12 is 150nf, 63v MKS caps. Can't find any BG caps with such value.
Sam