receiver vs digital preamp/tuner  

Hi,
I'm wondering how much of a difference a separate preamp would do compared to a receiver. I was thinking of getting a Denon AVR3801 with a separate 5 channel power amp, would replacing the Denon with a separate preamp, such as a B&K Ref 30 or Anthem AVM 2 produce much better sound? Are preamps really worth their price? (>3X the price of the denon, ouch!)

Are any of them upgradeable via software or plug in chips? I'm interested in DTS ES, which the Denon offers, but AFAIK not any of the 2 preamps(or any other preamp for that matter). THX EX would be nice too.

Thanks!

Hmmn, ok, but what I'm wondering if is it really worth the increase in price? Most preamps costs more than a power amp itself, and power amps are already more expensive than a receiver. Is the increase in sound quality really that apparent?

Thanks for the reply kotches, even though its a tad vague http://www.avsforum.com/ubb/smile.gif
I'm in fact working with a dealer to audition the Anthem MCA-5 with a set of Paradigm speakers(Monitor 9, CC/ADP-350 and PS1200), with my own CD player. However, the dealer doesn't have the Denon 3801. He's trying to loan it from another dealer, but no gaurantees. If that fails, he'll plug in a Rotel RSP985 or 976(?) to get a feel of the system.

So basically you're saying, in the case of the Denon 3801 vs either the B&K or Anthem preamp/digital processor, its going to be a noticable difference? What exactly causes the differences? I'm not very aware of what differences there are in the preamp section. I know that for the power amp, the type/size of transformers/capacitors, and the configuration(single power supply of multiple monoblocks), among other factors, affect the sound quality, but what about in the preamp? Is it simply the circuitry?

btw, I'm also considering(based on price/features) the Yamaha RX-V1000 and the Sony STR-V555ES. How do these compare with the Denon?