This thread went downhill extremely fast.
To the OP, if you currently have the standard HD that came with the Mini then unquestionably you will get the biggest bang for you buck from a SSD.
Have you ever take a look at Activity Monitor to see how much of your CPU you are using at any one time???? I'd imagine you are using less than 20% at any one time. I may be wrong as you did not list what you use your system for, but most people do not understand that adding a faster processor will often do nothing to improve perceived speeds.
Good luck. I just got the 2.4 i5 mini and am waiting on my SSD from OWC. I am amazed at how awful this system is with the standard HD and 4GB of RAM. A SSD, if you have not used one, will likely be the best upgrade you ever do.