the new wires wont reduce knock and unless they havent been changed in awhile (past 40k mi?) new ones dont do much. you say better spark plugs i assume you mean colder, copper plugs? yes dyno's do cost about 100 and the only other way to know if you car is taking to the mods well or not is to get a scaner that shows KR. my auterra scan tool shows hp and tq as well as 0-60 and 1/4 mi runs.
you really should read all of this if you havent already, it will answer alot of your questions
http://www.regalgs.org/forum/viewtop...43cb8374bb3a30