You can always mod the stock Busa cans by pulling out the chambered baffles and installing straight ones. Cost is around $20.00 and they sound pretty good.
i have a set of stock mufflers with the baffles knocked out, they do sound pretty impressive...
I have had a set of slip-on's, also had a 4-1 Arko, now got striped stock mufflers with 3" perferated tube baffled with 500g wire wool in each, BUT I have also removed the restrictive 2 x cat's in the downpipes, efectively a straight through.
They sound louder than the Arko but deeper like a twin, or in other words sound like a smoth twin if that make's any sence, and it looks stock.
As for power:
Between stock and race cans not that noticable slightly more peaky.
Then to a 4-1 Arko masive difference (night & day) more peaky and alot more power, easy power wheelie in second.
Then back to stock, so boring, second gear power wheelie not as easy, huge difference.
Now stock downpipes cut open with both cat's removed then rewelded can's striped with 3" perferated tube & baffled with wire wool. It feals like the Arko not quite as peaky but not much in it, power wheelie easy in second again, huge difference from stock. I think if it goes back on a dyno it will be within about 2bhp as the Arko 4-1.
I wanted a stock look, but wanted power, and nice sound. I dont like all black with black frame swingarm etc but it seam's to be the in thing, but the original bike in the thread does look fine if you like the black thing. Nothing wrong with it at all.
What do you all use to do a sound clip, i'm gessing your phone's. Hear is a sound clip with an Arko 4-1 on my busa, will do one with the modded stock soon.