In answer to your question about quality against a PS3, yes the Low preset looks similar to a PS3, and very close to a Xbox 360. I'd try these settings given your current spec and the size of your Monitor.
Resolution: 1920x1080
VSync: Off
Textures: Ultra
Shadows: Medium
Effects: High
Mesh: High
Terrain: High
Terrain Decoration: Ultra
AA Deferred: None
AA Post: Medium
Motion Blur: Off
Anisotropic filter: 2X
Ambient Occlusion: HBAO
These are the settings I set my girlfriends up and she has a similar spec to yourself, also using a 550ti OC but on a 24" Display. On a 1920x1080 display you really won't see alot of difference between using a small and medium-large amount of Anisotropic filtering (barely any difference at all). You should see around a 42-44 average FPS, but there are some spots in Operation Metro (around A on Conquest) that you will see a drop down to about 33-35 FPS. 64 player games shouldn't be a problem with these settings.
The frame issue you have isn't with the GPU, you will deffinately see a bit of a bottleneck from a Tri-Core Processor, but uprgrading for the sake of a few frames (and we are talking 5-10 frames here) isn't really worth the money. I'd plod on and save until sort of Medal of Honor Warfighter (if you're bothered about it) or BF4 and then do a full upgrade.
Hope this helps!