Smaller Caps
I for one do believe in a larger numer of smaller caps. I do not use so-called audiophile caps but good quality low inpedance units(Philips, Seimens, RIFA would be fine!). I have built a number of amps of 100W output with 2/3 pairs of power devices and I designed the layout myself. What I do is to use a piece of low impedance cap of between 4700 - 10000uF per device and the pcb is designed in such a manner that the legs of the power transistor solders directly onto the leg of the cap(sorry, impossible for TO3's!!) which is further paralleled with a piece of ultra low impedance 100uF electrolytic cap and a 2.2uF film cap(available from Farnell & RS). For wiring, each cap/output device is fed by a SEPARATE wire from the rectifier and also a SEPARATE earth return to the main chassis earth (kind of messy and reminds you of hard wiring in early tube hifi sets). This way, you avoid the eddy currents that bounce around when many devices share a common power and earth track. (BTW, if you try this, use equal wiring lengths for each device- I'm paranoid about connection symmetry!!)You'll be pleasantly surprised with the difference in sound when you listen to quiet passages. Details are more and the sound is lively and bouncy while big tin can size caps tend to give a heavier and more sluggish sound but killer heavy weight bass! You will also find that you can "tune" the sound by changing the small paralleled E cap and film cap!
If you're happy with the sound, you may want to try running separate grounds with a "star chassis ground" arrangement for ALL other parts of your power amp or at least run a separate ground for the input section. Mixing your signal grounds with the power supply decoupling caps ground is a strict no! no!
Happy experimenting!
ckt