Upgrading my build

Hello, I am currently running a Core 2 Duo E8400 @ 3.00GHz, GA-EP45-DS3L mobo, 8gb ddr2 800mhz ram, 1.5tb 7200 rpm hdd, hx620w corsair powersupply and Amd HD 6770 gpu at 1080p.

I want to upgrade to a pc that can handle BF4 on ultra at 1080p. Im not suire whether i should get and i5 2400+H77 DS3H(pcie 3.0)+8GB 1600MHZ ram or maybe upgrading my current cpu that is compatible with my current mobo and ram.

http://www.gigabyte.pk/support-downloads/cpu-support-popup.aspx?pid=2844
This is my mobo cpu support list, what cpu would you recommend? Would it be better than the i5 2400? Also, i wanted to upgrade to a r9 270x 4gb used costing me about $162. If i were to upgrade my cpu(lga 775) would i bottleneck my 270x 4gb?

Also, if i go for the i5 2400 build, should i go for DQ67SW(pcie 2.0) instead of the h77 ds3h so that i can run my current gpu on it in the future? The h77 costs about $28 more , and if i get the 270x 4gb in the near future, how much performance would i lose if i run it on a pcie 2.0?

Please help im really worried and wana get back to serious gaming as soon as possible.Thanks
 
Ok on the other note then, PCI-E 3.0 vs PCI-E 2.0 difference is insignificant. You shouldn't lose almost any performance. However you should go for the h77 since PCI-E is backwards compatible meaning you can run a pci-e 2.0 card on a pci-e 3.0 slot without a problem.