If you try to build a new system, you will not be able to get much more from it than the system you have now. Possibly with an AMD system, but not all that much better. Any new Intel with all new parts will be around $800 without monitor. That is an i5 with 8 gigs of DDR3 memory.
I think you should upgrade the memory and OS if needed. And then see where you need to go. That shipping is killer