Thanks Neilsouth. After a week searching for a definitive solution, just like most everyone, I was forced to give up trying to find a way to make Windows 7 send music to all speakers with same quality. And since I'm not willing to pay $30 for Creative software (see: Windows 7 RC 64 bit Getting Sound From 2 Speakers and Minor Questions
), I guess I'll have to wait for Realtek to provide a solution, as its 3DSoundBack, which is supposed to do the same as Creative's ALchemy, did not solve the problem either. I found yours was the only workaround for the lack of DirectSound in Windows 7.
In addition to this post, I found that in my PC these settings were in a different key (I suppose it's because of the driver version), so you might want to go to "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\" in regedit and do a Ctrl+F for "DevType_" and find the correct key for your version.
Also, in my version (R236) the "Pin01" controls only the rear speakers, and the "Pin03" controls the side ones. The "Pin02" was not present, but I add it and worked fine.
I set all output jacks to "Front speakers", this way I managed to have good quality sound from every speaker. The bad thing about it is when you want to play games with real surround sound, for all speakers would just play the same thing. My solution was to export 2 registry keys, one with the original configuration, and one with all jacks set to front ( or what suits you best), then just click the .reg files to switch between "real" and "fake" surround. To avoid having to restart the system every time for the changes to take effect, follow these steps:
1) Close every app which may be using the audio device (such as media players).
2) Apply the desired .reg file.
3) Go to Device Manager, select "Sound, video and game controllers". Right-click on the Realtek device and select "Disable" (if no app is using the sound you should not be prompted with the restart message).
4) Right-click it again and select "Enable".
That's all. I hope I could help some of the troubled people like me. I searched day and night everywhere and I was getting sick of this. At least now I have an alternative to this issue.