I would go a single in dual out setup, unless you run a supercharger/turbocharger you're destroying your scavenger effect with true duals. I have the Flomaster 50 Delta Flow SUV on my Expedition and it's all the noise I could want, my gf can easily hear it 1/4mile away when I step on it, but it's not too bad to listen to when I'm running 1,000 miles on the interstate (which I have to do tomorrow *sighs*).
Anyways, with your pickup, I would go Flowmaster 40 Delata flow for really loud, but if you're a crew cab with a family, I'd go more with Flowmaster 50. I know alot of buddies that get the 40 but it's just way too loud inside the cab to have normal family conversation. It's very aggravating to have to turn your radio past half way to override the muffler (I already have to do this to get passed the cabin noise, but I'm an SUV, they tend to be louder inside).
You'll see alot of people also recommend magnaflow or cherrybomb glasspacks. Again, mufflers are a personal thing, the sound for one person may be great and for someone else very agitating. I find magnaflows sound to be too hollow, almost resonating. I like the deep reserved growl of flowmaster. I don't want to sound like a carbed Mercury outboard, though they sound nice, I want a very structured, tuned, deep sound from my truck. As for glasspacks, I hate them completely, way too loud, and sound much like firecrackers. But again I like smooth deep engine noise, so glasspacks obviously move away from that.
Personally, I can't find a thing wrong with the stock muffler...and sound. Ford did a lot of research on that stock muffler, and when you get on it I think it sounds better than any stock muffler they've put out in 30 years.
Actually, I was thinking the same thing as you, as I had a Magnaflow SIDO on my '04 Lariat. I guess I'm getting older, because I've been doing a lot of research to see if I can find anything that will eliminate the cab drone. I remember how nice and quiet that '04 Lariat was before I did that...and now I'm enjoying the quietness on the highway again with the new KR. So, at least for a couple of years, I'm staying stock.
2009 F-150 4x4 King Ranch, Royal Red/Pueblo Gold, 5.4L FFV, 6-Spd Auto, Sony 700W Nav/Radio, Pwr Rear Window, Pwr Moonroof, Rear View Camera, Heat/Cooled Front Seats, Skid Plates, 20" Aluminum Wheels, Trailer Brake Controller. Added: SnugTop SnugLid TC tonneau cover, BedRug Bed Liner, Carriage Works Lower Bumper Grille, King Ranch Hitch Plug, Lumar Tint 20%, AVS VentVisor Window Deflectors.
I had Magnaflow on the old 5.2 Ram, and am looking at the same shop and product on this new 5.4 F-150. It sounds good, but it's not so loud inside that you can't listen to the radio or have a conversation. I also think it matters where you locate the tips yeah? I always put mine under the rear bumper instead of behind the wheels on the sides. I like to put them as far back from the cab as possible. I know it sounds good; it's personal preference.