My answer won’t be great because I don’t know specifics about what you’ll be using your system for… but…
if you have good peripherals (montior, kbd, mouse, spkrs, etc)
you can simply replace the main system..
if you’re good with computers you can build a decent setup for under $1000 with parts from a cheap source such as https://newegg.com
I’d suggest multiple core cpu(s), lots of hard drive (at lest 300+ gb) and gobs of memory as well as a decent gaming video card (I say gaming because just about anything that’ll work for gaming works great for graphic arts).
if you DONT know how to build a pc, DELL makes some decent systems, or from what I hear the new apple’s aren’t too shabby either, but I’m a pc person.. soooo…
Hope this helps..
-Jeremy