I have the area rug already. Having the m-5140 I noticed I have 2 channels with 4 speaker lines. Can I use two lines for bookshelfs and the other channel for a passive sub?
On an unrelated note - I am beginning to notice that the true quality of sound is limited by the reproduction and source of the music. i.e vinyl, cd, and the people who reproduce it. I have noticed a real difference in the vinyl moreso the cd's. I prefer live albums because of the content. Have you noticed a recording company that stands out with their reporductions?
That plan will not work. First A & B speakers use the same power amps, so your plan will drop he impedance to your amps too low and damage them. Passive subs will have no crossover, so your sub will be driven full range.
To integrate a sub with a two channel system that has no bass management (pretty much all) you need a pre amp/power amp combination. Then you take out the preamp outputs to the power amp and with a Y connector take one side of the Ys to your power amp, and the other to a 2/1 buffer amp and then to either a powered sub with crossover or an external crossover and another power amp to power a passive sub.
If you can get a powered sub with left and right inputs it will do the buffering for you and you can connect with Y connectors to your power amp and to the powered sub.
If you don't want this hassle, which by the way is not as complicated as it may at first seem, then you need a multichannel receiver, that has bass management. Of course you would only use the left and right speaker outputs, and connect to a powered sub via the LFE output.
You should note however this will not be the same as receiver bass management unless you use two way electronic crossovers. With just a low pass crossover your left and right speakers will run full range.
Unfortunately I think there should be an abundance of 2.1 receivers with bass management and preamp set up similarly, but for reasons I fail to understand there are not. If there were, that would be your solution. I suppose in modern manufacture it is cheaper to build a lot of receivers with 5 amps and have customers like you not use three of the two amps.
If I were in charge of a manufacturing line, the first thing I would do is make a slim elegant AV 2.1 pre/pro and a 2.1 AV receiver, with a smaller profile than current offerings.
But then again, if I were in charge an awful lot of things would be done differently from the way they are done now and everybody would be the better for it.
As far as recordings, vinyl has always had a wide variation in quality. In the classical arena CDs are pretty much uniformly of high quality. I note a lot of complaints from the pop fraternity however.