At this point would like to summarize the suggestions or approaches to maximize a speaker:
(1) Use of snubber circuit - to reduce high frequency peak voltage; subjectively to minimize sibilance.
(2) Use of choke or inductor - to improve rate of charge/discharge of current; also a small choke stores low amplitude signals better; subjectively to improve mids and highs.
Since this may not be enough for some people would like to offer one approach to improve on item 1.
It would be a good idea if the signal being "improved" by the snubber is made "better". To do this we will be using the time tested approach of using smaller and better capacitors placed in parallel with C1 and C2. So that it is cost effective we will just put 2 capacitors in parallel.
Edit 11/07/2010
Here are some suggestions ...
(1)
C1 and C2 = 220uF, place a 2.2uF/50V (electrolytic cap) and 560N/50V (mylar cap)(2)
C1 and C2 = 270/330uF, place a 3.3uF/50V (electrolytic cap) and 680N/50V (mylar cap)nb You may use better capacitors if you want