Dont go with crossfire man its not worth it, same with Sli. Also dont go with dual core, not unless your doing video editing or music editing or soemthing of that sort only. You can save some more money and put it towards your gpu and buy a x1900xt 512mb or something.
Id buy a X1800xt 512mb if i were you with a Amd Athlon 3800+ and overclock the **** out of it. And if you need more money for the upgrade to a better gpu such as a 512mb card which will be really useful in games you can buy a 80 gig harddrive and save god knows how much money. Ive had this 80 gig for 3 years now and havent used all the space on it. If your good at knowing what stuff you need and dont need anyway.
Go with a Antec power supply. With that system you want a good power supply, not a decent one. If you want to take risks with crappy power supplies you might as well put some socks on and rub your feet on the carpet and touch all your hardware components.
Thats my advice. Its your money if you want to make a bad decision do it, but dont get ****ed off if you later find out you spent more money than you should have.
Its a nice system what you chose though, Nice job by the way