actually, a2 would probably sound darker than the a8. imo, if you want bright, try an a3. it's like a2 with alot more treble(a favorite of mine in the neck spot

). as far as a8 vs stock, i think that would be a good choice if you were to take out one or both of the side ceramic magnets in there, smoothing out the response and having full on a8 in there.
the only thing to watch out for with a8 is to make sure you don't have it too close to the strings, just like with the ceramics