I have the 2400 and have it bi-wired to my 60's and it sounds great. The only problem being that I didn't listen to it without being bi-wired so I can't really compare what the differences would be.
I'm no expert but if I understand correctly bi-wiring splits the signal so that your mids and tweeters are fed by one connection and the subs are fed by another. I think it's supposed to result in a cleaner sound.
I haven't listened to a lot of recievers but I know I love my 2400.