Upgradable?

Yes to both the video card and power supply.

I was reading into the specs and it says (1) PCI Express x16 (occupied) which the gpu would need. What do you think is using that slot?

The only thing typically installed in the x16 slots are video cards. I see what you are looking at. I assume (since this model uses integrated video) that this is a typo.

I found a different one for about the same price and better specs http://www.qvc.com/ZT-Desktop---Intel-Core-i5-3470,-12G...$uslarge$

This one has a GT630 that uses a pci 2.0 slot. How much would that effect the performance of a 3.0 card like the 7870?

For all practical purposes, the difference between a PCIe 2.0 and 3.0 slot will have little bearing on the performance as seen by the user. Installing a HD7870 into the PCIe 2.0 slot, for example, will have minimal measurable impact.

Essentially, this really isn't an issue.

Alright good now the only other problem i see would http://www.newegg.com/Product/Product.aspx?Item=N82E168... be able to fit into the case. the case measurements are 7-1/8"W x 13-7/8"H x 16-7/8"D.

Has be bought it yet? For the price of the computer alone you could make a build to incorporate a 7870. Is be opposed to building a system himself? Maybe with your help?

I say build your own too. Save cash, learn and have fun with it. It really isn't hard to do, you just have to dive in!

The reason for buying a prebuilt one from that website is for the monthly payments

It says http://www.qvc.com/ZT-Desktop---Intel-Core-i5-3470,-12G...$uslarge$ Come with an AC adapter? This is very nooby but is that like a laptop power supply or is it just the wire?

The UL power info is just a standard power standard and doesn't refer to a power supply like a laptop uses. No worries there.

The length of the HD7870 could be an issue. There is no way to verify without measuring inside the case. It certainly looks big enough to accommodate it.

More info on the system can be found here:

http://www.ztsystems.com/default.aspx?tabid=1239&produc...