Well, I'll just post one more thing on the subject. I think it's a lot of personal preference, and what you have done to the motor, I'll still contend that on a fairly stock motor the cost of a head pipe verses the HP gain is about $150 per horse. I can spend that some where else. Below is a note from night rider, here I go again, with the night rider stuff!!!
You actually have called the best combination for most bikes. The OEM header pipes and slip-on mufflers is the most cost effective upgrade you can make to the bike. All OEM HD header systems are based on a Cross-over pipe. The cross-over pipes is a well known trick to improve the low/mid range performance of an exhaust system by improving the overall volume contained inside the exhaust system. The larger the volume of the exhaust system, the harder it is for the exhaust system to restrict flow and reduce power when the engine is under heavy load. For those naysayers that might indicate that x-overs hurt power, all you have to do is look under any American muscle car to look at the exhaust system. Corvette, Mustang and virtually every other performance vehicle uses cross-overs to improve power.
So the simple slip-on muffler is going to result in the best average power in the low/mid range which is where you spend your time actually riding the bike. This generally applies to engines making up to 1HP/ft.lb./CID.
There will a few who say that True Duals will make better HP. This may be a true statement is some conditions, but the torque and average power is generally not going to be up to par with the simpler upgrades. There are always those few who want bragging rights at the local watering hole. But these also tend to be the guys who throw money at their engines, then complain when the don't get the power they expected, but spend all their time telling you how to build an engine.
There are always circumstances and situations that you may want to use other exhaust systems. True 2-1 systems and 2-2 systems can have interesting scavenging characteristics that can improve power in certain rpm ranges. But you need to know what these ranges are, build an appropriate engine to optimize these ranges, carefully build an engine to the correct specs, the spend a lot of time on the dyno tuning the engine. These "superior" engines can benefit from other exhaust systems, but superior power also has a superior cost, it is all in the details.
Bottom line is there never will be a bottom line, people will always have different opinions on this stuff, that's why there are sites like this, so we can get different perspectives!