What Computer should I get?

You're not going to get anything that can run the latest version(s) of Premiere Pro at all at that budget, especially not a pre-built PC:

1) That new PC for that low will give you a CPU that is actually slower (performance-wise) than a 10-year-old low-end CPU.

2) At that price you will not get enough RAM to run Premiere Pro CC at all. Premiere Pro CC requires a minimum of 8GB (preferably 16GB) of installed RAM to even run at all. You'd be lucky to have even 4GB of RAM - but more than likely you'll have only 2GB of RAM installed.

3) Don't expect an SSD in a PC for that low of a price. Instead, you'll get a hard drive that's glacially slow, especially in random operations.

4) Integrated graphics which may or may not be supported by Premiere's hardware GPU rendering engine are a given. Do not expect a discrete GPU in a PC priced this low.

And all this is due in part to the colossal retreat of AMD from the CPU performance race in recent years. As a result, new CPUs from Intel have crept upwards in price at every given performance grade.