reciever vs seperates

Can someone either explain to me or point out a link that analyzes the differences between recievers and seperates? Specifically I know that seperates consist of pre-amps, amps, dacs, surround sound processors; what do each of these do? And more importantly which is likely to improve the sound over a standard reciever?

For example, I have a denon 3803 and i've heard that they don't have good dacs. Can I add a dac into this configuration and would it make a significant difference in quality. Which seperate is likely to increase quality the most over a reciever? thanks
For me, the major differences between the two are control, capability of dedicated circuits, and ease of upradeability.

Control - A good example of this is an outboard amp. A decent amp will provide better control to your speakers as far as bass, mids, and highs. I doubt it if there is a receiver that can match the "control" in speakers of 5 outboard amps(5 each and separate power supplies, transformers, memory, not to mention total power)in a 5 channel set up.

Dedicated circuit - A DAC is a good example here. A separate dac (MSB or Monarchy which are not expensive at all) performs better than any DACs on three receivers (Yamaha RXV-1, HK AVR 8000, and Onkyo TXDS777)that I had the unfortunate experienced of owning/auditioning. I kept the RXV-1 as a processor and bought a separate dac and amps for 2ch-5ch listening on my HT system. Of course, the manufacturers of these receivers have the capability to improve the DACs but the biggest limitation is the real state it will take for the circuit design inside the receiver. Remember, inside the receivers not counting the DAC, you still have to accomodate processor circuits, display and control circuits, several channels of pre-amplification and power amplication, power supplies, wirings etc. In short, outboard DACs are way better because that's all they do and there is no compromise. All the design and improvements are aimed at one purpose only, that is to improve its Digital to Analog conversion capability

Upgradeability - This is self explanatory. For separates, you can hand pick (or ear pick) the preamp/processor, amp, dacs, and cabling to your liking (or to your wife's liking). On a receiver, what you see is what you get (WYSIWYG)! Although, you can always improve amplification by buying a separate amp and using your receiver's pre-out capability. But would that mean you are "quasi-separates" already?

Of course, the descriptions above were my experienced when I was in the "receiver" state of mind. I will never go back to it IMHO since moving to separates is nothing short of a revelation to me. inform, not to convince....
So would you say that the weakest link in the reciever is the dac? If I added a external dac to my set-up would this provide the greatest improvement in sound? Can I set it up so that I use an external dac and a reciever?? Thanks
Greatest improvement in sound? What are you trying to accomplish? Might want to post the rest of your system so some of the more experienced on this board can give a more informed explanation of their suggestions.

I used a denon 2800 for around 5 years and decided about 2 years ago to search for higher quality sound. Started with a seperate amp for my front L & R speakers and the difference was impressive. Cleaner highs better bass, etc. The most startling was low level coherence. We no longer had to listen at high levels to get a feel from the music. I am sure the amps in the 3800 are much better than in the 2800 but would suggest an in home audition of both the DAC and an amp for you to determine which initial direction you want to head.
The DAC (digital to analogue converter) will go between your digital source (cd player, dvd) and the reciever. Having never used an external dac I have no opinion other than to say I too have read about them and would like to give it a try.
I have:

Mangepan MMGs
Denon dvd 1600
denon avr 3803
and monster cables.
Ohh .. I missed you other question.

I'd like a bigger sound stage (more projection from the speakers) and ability to listen at lower levels and still feel the music.
Might try here for lots of info on mmg speakers. Have read that position is critical and many users tilt the speaker down toward the listening position. They are very revealing of upstream components and bad recordings. Be sure you are using a good quality recording while experimenting with placement. Would really consider trying an external amp. May give just what you are looking for after proper placement. Do try the link. There are so many there with hands on experience with these speakers that you should be able to get some good info and probably some there are using the 3802.