Hahaha, Pramod, here are my answers:
- Generally speaking, when one gets a component that does one specific job, all the attention and engineering budget is put on getting that part right. Like, if you see most power amps, they will have rating of 100W RMS (and upwards) whereas integrated amps will generally have 45W, 60W etc. The other interesting thing I have found is that power amps are available for far lower prices in the used market. Not sure why. Maybe because supply/demand - people generally prefer integrated amps so they are priced higher and command higher prices?
I had a Parasound power amp that I bought for a ridiculously low price ($350 for a 6 month old amp - new was costing $850). That amp was so powerful (while being fairly compact as well) - it would drive any speaker with ease and not even get heated up. Generally, the strong amps - you will see power rating scale linearly. Like if an amp does 50W in 8 ohms, it will do 100W in 4 ohms (and even 200W in 2 ohms for really difficult to drive speakers). Amps with weak power supplies will only do 70W in 4 ohms for example - or will even state upfront that they cannot support anything below 8 ohms or 6 ohms.
Now most speakers cleverly only state nominal impedance. Your speakers are 6 ohms nominal - but I can bet that in reality, it dips down to 4 ohms in some audio frequencies. This means that your amp needs to have a powerful/robust enough power supply that it can handle the 4 ohm load with ease as well. Many, if not most speakers, dip down to 4 ohms routinely. With weak amps, they start failing to provide adequate power at these impedance dips and in extreme cases, start clipping (pure DC signal) which can damage your speaker drivers. That is also why overkill on the amp side is actually not a bad idea. My old Parasound amp for example would do 125W in 8 ohms, 200W in 4 ohms, and up to 400W for 2 ohms.
- External DAC - From personal experience, AVR DACs are decent enough. A discrete DAC would still be better of course, but now it depends how much quality or musical flavor one wants. My Audio GD DAC was significantly superior to my Marantz slimline AVR, but I am happy enough with the Marantz inbuilt DAC for now. M room and speaker placement is suboptimal anyway.
2 - 24/192 - that is mostly bragging about features - it is about high-resolution audio formats. It has become the new buzzword. It refers to the DAC's ability to process audio that has been encoded in high bitrate formats (24 bits at 192 khz). CD audio is encoded at 16 bits at 44KHz. That is actually supposed to be more than sufficient for human hearing, but as you know, audiophile loves overkill in everything. Personally, I find it irrelevant.
Truth be told, this is marketing gimmick. DAC quality is largely governed by the quality of its power supply, the quality of implementation (design), quality of parts used (not just the DAC chip, but even capacitors, etc). But that is unfashionable - so marketers sell DACs by bragging about bitrate support instead.
In fact, many people prefer older DACs because most of the money in old DACs was spent on power supply etc. and matter of fact, some people even prefer the older DAC chips (they feel the newer ones sound more artificial).
- The ability of a DAC to process high resolution audio (24/192, 32/384, etc.) has nothing to do with mp3 bitrate. This is difficult to explain but I will try. When analog audio is converted to digital audio in the studio, it is stored as uncompressed digital samples. The 24/192 indicates that they use 24 bits to store each sample, and sample the audio signal 192,000 times a second. (Audio CD stores audio sampled at 44,100 times a second, with 16bits to store the value of each sample). This is uncompressed digital bitstream.
However, this takes up a lot of space - CDs take up 600MB to store 60 minutes of (uncompressed) audio. High resolution audio like 24/192 takes way more (several GB) for the same. To save space, mp3 came up with a lossy compression format (a zip file is a lossless compression format). The bitrate of mp3 determines how lossy the compression is - i.e. how much sound quality do you care to lose to achieve more and more space saving). 320kbps gets really really close to original CD quality (16/44) - and for entry level systems like ours, or rooms that are not properly setup/treated, I don't think we will even notice much difference. But again, like everything, this is subjective, right?!
Ultimately, mp3 or any other format has to be converted back into the original (24/192 or 16/44.1) digital bitstream. DACs only understand this. If you feed mp3 into a DAC, it will not know what to do. This conversion is usually done in software (mp3 player like winamp or foobar in a computer, or a device/audio player that supports mp3).
So think of mp3 like a zip file. The real digital audio is the file inside the zip file. The zip file has to be unzipped for you to feed it into a DAC.
