CPU bottleneck?

[Hencore]

My current rig is

AMD Athlon II X4 Quad Core 630 2.80GHz (Socket AM3)
XFX HD 5830 1GB - GDDR5 SDRAM


It's starting to struggle with newer games and I'm looking to start upgrading.

Ideally I'm thinking i5 4690k+mobo and a GTX 970 but I'm a bit strapped for cash at the minute.

If I was to just pick up the gfx card first would my current cpu be a bottleneck?

 

[Hencore]

but that said for 970 cash, you can get an i5 and motherboard

Exactly but I can't afford both right this minute so trying to work out which is going to give me the biggest boost.