well guys i'm not geting all over amd here because i'm about to build an amd64 system, but, the p4 is better at multi tasking and video editing. they are both great chips and will suit you fine. go with wich ever one you can aford. i may be wrong but is there like a benchmarking comparison thing? like for example, if you wanted to test how two future systems would work...ie the amd and the p4 mentioned above...could you just do a comparing thing to see wich runs better? i know there probaly is one just that's another way to decide performance. if you are not going to be doing heavy gaming, doom3, hl2...yadda yadda yadda, get the p4. if you will be playing those games i suggest the amd.
as far as the vid card goes you don't need a new quite yet, i say wait for prices to go down on the new cards that are out.
my dad has a p4 system and there hasn't been any problems with the cpu, again both are great buuuuut i still think you should be goin with the p4. and don't forget about the RAM, value ram will mess with your computer!
best regards on your choice...just get what ever suits you, remeber if you aren't happy with your buy then it wasn't the right one.