hmm... nice opening statement. (nobody makes you post by the way) 8) (nothing to be angry over)
anyways..
1.) I asked what I am trying to 'get to' (achieve) in the LTSpice simulator (having never used it before.. and explaining I am new/not very experienced in audio stuff!?)... I changed the values.. and see 'some' line changes as well.. I also explained the results I got, with what values..etc.. but if I am not clear on what RESULTS I am trying to achieve in the top portion, I am just changing values for fun.. hence the change in the values on the board to 'hear' the changes in real life as well.
now, either you didnt read fully,..or you dont understand? .... "but I will repeat for emphasis." 
2.) If the cap I am changing out is NOT IN THE BREADBOARD, I am failing to make the connection about your 'plate' comments and pics of the internals of a breadboard?.. or how extra capacitance is being added???
instead of soldering the cap (C18) to the board, I have female terminated leads going to the cap instead. (I guess a flexible 'socket' if you wanna go that route.)
at this point...the only part in the breadboard.. (which I guess could also just be connected to wire/leads directly, although they dont fit very tight, so I used a breadboard to secure my connections.) is the POT for R5/R6 (nothing to do with capacitance).. so why the condescending tone? (I'm just looking for guidance from those more experienced then myself).. so back to what are you talking about for the breadboard/plate point? You are now talking about the POT? (which is resistance?)
Using a lower value cap for C18 as Wawa suggested/explained to me, did in fact, increase the quality of the audio..(from what I already considered pretty decent for a little hobby board)
the other board (which did not have a switchable/variable cap for C18) was not sounding the same as the original board.. it only had swappable parts for R5/R6 and R8.. which as explained (doesnt have anything to do with audio quality or capacitance, but mostly the volume).. hence my comments that that board must have a different value cap for C18 that I 'fat fingered'. the SMD value or something..