Joshman
dont listen to reason- if you can afford it go for it!! (hopefully my wife doesnt read this!)
I'm in the same position as you- ive got a 400D and happy. But unlike in the days of film when the camera was just a lightproof box and it was all about the lens, its not the case now. I am resigned to having to upgrade every couple of years- unlike my film cameras which I held for 5 years each (EOS 5 then EOS 3). Not to mention my MF folders which were 50 years old and my absolute favourties.
I dont know which way to go re 450 or 40. The big improvement for me would be live view, and the only reason I'm hesitating with the 450 is switch to SD cards. Factoring that cost of new cards into the equation and the 40D looks good (as well as better build but I am very careful with my gear- rain is my only enemy.
The 40D can be had at Discount Digital for $1260 or $1340 with kit lens. I bought this lens by itself a few months ago and after some testing it has replaced 3 primes!! Its very sharp and contrasty. Still need the 50 1.8 for wide aperture but at f8 the new 18-55 IS is as good as most of us need. (even though as I type this I cant get my mind off a 35 f1.4).
http://www.d-d-photographics.com/canon40d.htm They also appear to have a Brisbane pick up.
My bottom line- I'll probably procrastinate and like you my good judgement will keep the 400D in my bag for another year..
Robert