What to buy: New CPU or GPU?

Hey everyone.

Im new to ISboxer, and im currently boxing Diablo 3 with 3 chars.
EDIT: Im streaming on twitch.

i7-2600(non-k)
GTX570 1.2GB
16GB DDR3
Asus p8h67(the anti overclocker)

My problem is, I ran 2 chars decently after a few hours of tweaking, but now with 3 running, I have a little bit of trouble when theres alot of things going on on the screen.
CPU:
2chars: 80-100% - lagfree
3chars: 80-100% with lag in major battles
GPU:
2chars: 60-80% + 600-700mb vidmemory
3chars: 60-100% + 900-1000mb vidmemory

I cannot figure out what is my bottleneck here cause both my CPU and GPU run high up there.
Any advice, tips or tricks?

[lax]

Well, as far as your CPU I don't think you should have a problem at all with 2 or 3 or even 4 characters. If CPU is an issue for you, you may be able to solve it by adjusting CPU Strategy. In your case you should probably have all game instances set to use all cores (when ISBoxer 41 comes out, it will automatically default to this for you instead of Round-robin which will under-perform in this case).

I have a little bit of trouble when theres alot of things going on on the screen.

I would probably take a closer look at the performance of your GPU when you're running into trouble. From what you said I would expect that the GPU load % is going to spike when there's a lot of things going on on the screen, and when it is sitting at 100% is probably when you're experiencing the lag. If you run Open Hardware Monitor while you play you can put widgets on your screen (even somewhere over the game window) to try to keep a good eye on it.

I forgot to mention a very important thing.. Sorry about that.

Im streaming this on twitch..

Without the streaming everything is kinda smooth - can still feel the lag a bit when running into the big group of monsters.

But, when im streaming, if i open up a video window in xsplit or preview window on twitch - it drops my fps by 20-30fps.

But streaming it self eats majorly CPU if im correct..?

[MiRai]

But streaming it self eats majorly CPU if im correct..?

Yes, the CPU is used for encoding the stream before it's "uploaded" to the streaming site; so, the more that's happening on screen the harder it will be on the CPU -- This includes video settings and resolution, as well. However, I would guess that the 2600 should be more than enough to handle multiboxing the game and streaming at the same time.

I doubt XSplit has implemented a feature to use CUDA or OpenCL for utilizing the GPU to help encode, and even if they did, I would bet that it would be a separate option that would be off by default and the user would have to specifically enable.

However, the GPU pushing 100% of its usage should be throwing a red flag. I would try turning down your video settings in game, your background/foreground FPS (most people use 30/30), or your resolution.

[lax]

Okay, that does change my recommendation somewhat as far as your CPU, yes.

Real-time video encoding is indeed going to be heavy on the CPU. Newer CPU generations may also improve performance specifically for this type of activity. I don't have a specific CPU recommendation but you would probably be well served by additional CPU cores (e.g. a x6 instead of x4 CPU).

It would probably also benefit (smooth) game performance to limit the video encoding to one set of CPU cores, and the game instances to another set of CPU cores. (Having more CPU cores as mentioned above would, of course, help with this overall.)