Diesel Bombers - Dual Stacks kit

ok so I am presently deployed to Iraq and my wife is on a mission, and pulling me behind her on this. She fell in love with dual stacks on trucks (thanks youtube), and since i was getting ready to pull the trigger on buying an exhaust she sprang in with the I am buying them so i want stacks, more specifically dual stacks.. aussie or bullhaulers (preferred). so looking around online best price she found was for a 4" Grand Rocks kit WITH dual 5" aussie tips for $470.00 shipped, which is a great price, but if there is a chance I can get them cheaper then by all means i should take advantage of it right? So my proposal is, I am asking fort vendors and manufacturers quote me the best price they can. Please help me out, and make my wife happy of the present she is getting me for my birthday!