I wouldn't think that the muffler design would be much different from the single vs. dual tip. I have the Stillen "Bull-nose" single tip and I find the exhaust note to be very bearable with my split d/ps and t/ps. There is no noticeable resonance either. I prefer a mellow sounding exhaust note over an obnoxious fart can.
'03 Nissan 350Z Touring 6 Aero Super Black '97 Nissan 240SX S14 SR-Turbo Obsidian Black Stage X '90 Nissan 300ZX Twin Turbo Aztec Red Stage XII '05 Chevy Avalanche LT Black (Daily Driver)