"Bhain333":
I think that it would boil down to what type of sound do you want. If you want a cleaner and more refined sound, then I would go for the Yamaha RX-V2400. If you want more power and definition (lacking a better word) with bass punch and slam, then I would go for the Denon AVR-3803.
I am in the process of upgrading my home theater system also, and I am getting a new surround sound receiver as well. For a while, I have been interested in the Yamaha RX-V740. But now that newer upper line models such as Yamaha's RX-V-1400 and RX-V2400 have recently hit the market, I am sort of intrigued with the RX-V1400 myself, and am thinking about auditioning that model before finally making a decision. The RX-V1400 is $200.00 more than the RX-V740, and what I want to know more than anything is what do I stand to gain for $200.00 more dollars by going with the RX-V1400 over the RX-V740. My room is rather on the small side, so I am not going to need the extra power in most cases (110W x 7 for the RX-V1400 vs. 90W x 6 for the RX-V740). And I don't know whether I am going to be using the extra features as well. I know that if I won't be using a whole lot of extra features, nor if I wouldn't need the extra power so to speak, then I am going to end up with the RX-V740. But that's just me though.
So then, I would say go ahead, listen to both (the Yamaha RX-V2400 and the Denon AVR-3803) and see which type of sound from both of these receivers appeal to you. And then I would narrow it down to features. Which ones you think you'll need the most vs. which ones you can do without. I would then base my finally decision on that criteria.
Good Luck and Happy Shopping........
--Charles--