In general, from what I've read and experienced, that 0.1 uF cap, and the 1.0 uF cap, are the most vital to the sound of the amp. Changing these to any high quality audio cap should be one of the first and most beneficial mods done. I found their contributions to be comparable to one another, and greater than changing the 1000 uF or 47 uF PS caps, or changing the bias resistor to a resistor + LED, though all of these had some measure of impact.
Of course, I am something of a newbie to all of this, but you can read my impressions about the Obbligato golds and Russian FT-3 teflons in a thread I started about caps below.
It's also a simple matter to find a number of reviews with comparisons between audio grade caps - just search for "capacitor shootout" or something similar.
Best of luck,
Guy