Im liking that side exit with the rectangle tips!!
The cheapest way would be to find a muffler you like (try youtube).
1. By what you said a magnaflow 18" muffler would be what your looking for, not too lout but a nice deep rumble. Single 3" in and dual 2.5" out is what youll need. ~$100
2 . Find some nice tips(stainless will last much longer) 4x12 would be a good size since you dont have cut outs.~$75-$125
3. take it to a muffler shop and have them make up some pipes and install it. The price varies greatly on where your located, ive seen some crazy numbers on here people paid for a simple muffler swap. A fair price would be in the $150-$200 range
4. Start that thing up and enjoy!!
12 RCSB Express- 5%Tint, Gatorhyde spray-in, Black OEM Tips, Plasti Dip badges and Interior, CBE muffler,AFE CAI, Kenwood DDX370, Ks3.5s, Pioneer 6x9s,BT 964SP lowered on oem chrome 17's and some LEDs... Plenty on the To-Do list
New audio build in progress