DDR2@333Mhz, E4500@2.2Ghz, PCI-E2.0 - what bottlenecks GTX 970 the most?

[meetyomaker]

Hi dear THW community!

Recently, I had to leave my main accommodation for a far-far away place where there is an ancient PC of mine:

ASRock G31m-s (has one PCI-E2.0 x16 which accommodates GTX 970)
Intel Core 2 Duo E4500 (@2.2, not overclocked)
2Gb of DDR2 @ 333Mhz (2x1Gb dual-channel)
Windows 7 HB 32-bit
SSD Kingston SV300S 60Gb (system only) + HDD Hitachi HDP725050GLA360 (500Gb, 7200 rpm, 16mb cache)

In a hope to spare some time playing Dota 2, I brought MSI GTX 970 and Corsair CX750M with me. Here is - you guessed it - the punchline: the game runs like crap @1080p with 15-30 fps at any settings. Lower resolutions do not result in anything more than stable 35 fps. In fact, 35 fps are achieved on the minimum settings @768p.

Here is the question: which part of the old rig bottlenecks graphics the most? RAM, CPU or motherboard (unlikely)? Will going for 2x2Gb @800Mhz in dual-channel help the situation?
Overclocking CPU is not preferable since its cooler is unlikely to handle even 2.6Ghz under stress.

Nvidia driver ver. 361.43, Dota 2 is installed on the HDD.

Any suggestions appreciated.

 

[Deleted member 362816]

The cpu is a huge bottleneck along with only 2gb of ram.

 

[meetyomaker]

The cpu is a huge bottleneck along with only 2gb of ram.

So will going for 4gb DDR2@800 be of a much help without replacing CPU?

 

[Deleted member 362816]

The cpu is a huge bottleneck along with only 2gb of ram.

So will going for 4gb DDR2@800 be of a much help without replacing CPU?

It will help but everything in this build is going to badly bottleneck a gtx 970.