I think another key portion of this discussion has to center around other parts and component questions, i.e.:
Do you require the monitor, keyboard and mouse that come with the Costco rig? If you get into building an i7 box, these may add to your expense.
Is the Costco rig at all upgradeable? In my experience, pre-built boxes are difficult, at best, to work in.
What is the quality of the other components in the Costco box? If it is using lower-end parts, the machine might only last a year or so, and generally there isn't much salvageable from pre-built rigs (again, my experience, may not be entirely true).
The other key part to this question lies in being honest with yourself about your desires. You state that you want to get into certain activities that require some fairly high-end work to take seriously, but you are looking at a $1000 budget. That budget doesn't tend to go well with taking video editing and other resource-hogging application work seriously. Can it be done? Sure, I think. But it would take some effort.
If this is a casual, potentially passing interest, I'd actually suggest spending a little more than the $1000 and getting an iMac. All in one and generally ready to do everything you are interested in out of the box with little to no additional software costs.
If this is a serious interest, I'd recommend busting your butt to get your budget higher and run with an i7 with 6gig's of ram, a very high quality hard drive (think WD Caviar Black), and a moderate to high-end video card for the animation and video editing.
If your interest lies somewhere in between those two, look at building an i5 machine on a motherboard that supports both the i5 and i7 chipsets with two PCI-E slots and a very decent power supply. This will give you headroom for upgrading your machine as your interest becomes more serious and can easily be built under your $1000 budget, including monitor.
My final piece of advice would be to find someone knowledgeable about the activities that you are looking to do on this machine and ask them about their hardware. People who are serious about animation and audio editing are usually very serious about their hardware and will have a much better idea of what you need in relation to your level of interest.
Facebook
Twitter
Instagram