PC component price/performance is getting better constantly.
If you wait for the next best thing, you will wait forever.
If you have a need today, buy today.
Yes, Maxwell is coming, but starting at the lower end. Top end cards will not be here until the end of the year.
If they truly are outstanding performers, their price will be at a premium.
Your budget will buy you a very competent new pc.
Post a prospective build with links to where you might buy.
In principle, spend(for a gaming system) 2x your cpu budget for your graphics card. It is that important.
For example, pair a i5-4670K @225 with a $500 GTX780.
The i7-4770K chips are slightly better, but not worth the $100 price premium.
Few games can use the i7 hyperthreads.
I will not build today without a SSD for the "C" drive. 120gb at least, 240gb is preferable.
Use your old hard drive for storage of large files such as video's.
Anything faster for a cpu is pointless, A GTX780 is as good as it gets with a single monitor.
If you are planning on triple monitor gaming, or a 4k monitor, then things get much more expensive.
Buy only a quality psu.
Here is a list for guidance:
http://www.eggxpert.com/forums/thread/323050.aspx
You will need 575w for a GTX780. I like to overprovision a bit, say to 650w or so.