Passive Pre-amp: Improves overall sound quality??

I am not sure if a good TVC needs a particular cable or not. For me, I kept using the existing cable. But the most important aspect of a TVC (passive), I learned was the "gain" aspect.
You have to be absolutely careful in selecting the amp (and speakers - which I consider secondary) that you will be using with the passive. I was looking for a very good amp which was highly sensitive. the lower the sensitivity number, the highly sensitive it would be. The Parasound that I have has a sensitivity of 1V for full power (250 Watts). There are other amps that are more sensitive than this amp - but they are all tubes, and I did not want to go that route. When I got the combo in place, it sounded better than the integrated I had in place. But when I moved to the new room and wanted to place the speakers 4 feet in front of the wall, I missed the bass and body.
It was only when I moved up to XLR, that I actually got the "body" of the music that I was missing. I have my speakers 4 feet from the front wall and 30" from side walls and find that I have a great bass. Honestly, it is a night-and-day difference in my system. I believe this is the body and impact that Atmasphere is talking about. But again, it was a "gain" issue. Most people whom I have interacted with before, use TVC with tube amps. So, gain is not an issue for them, even when they use RCA.
I would be more than eager to compare my TVC with the Parasound JC2 preamp to see what more an active preamp can do in the system. If at all I upgrade the TVC to a active preamp in future, it will be either this preamp or the newer version of JC2. But my next upgrade will surely be CDP/Transport with a balanced output, that will ensure much more gain in my system.

Atmasphere, Anyone who spends $10,000 on an IC has a problem no pre-amp can cure. :)

Here's my recipe for building a system around a TVC: Start with a source capable of 4V output (XLR) with output impedance below 100 ohms. Amps (Plinius) have 38dB gain in balanced mode. Genesis 350 speakers are anything but shy for bass and slam. Easily capable of concert level SPL's. I have cheap cables.

Brownsfan, I think I agree with you; I have seen this, but really I used that example to make the point but it was also something I had experienced (BTW the person that had those cables was ecstatic that he was able to sell them and actually have better sound at the same time).

Atmasphere, I am not sure I understand the "5. = control the effect of the ic" if it isn't already included in the 4. ie the low output impedance sees the ic's impedance+amps input imp.