Need some help with upgrading - Should I do this?

[cassu]

Hey, this is my first post on these forums, regarding to upgrading my computer. I were looking around a place to ask from people who possibly know. So I hit this site.

Okay, so, I have HP G5120sc, link for it:
http://h10025.www1.hp.com/ewfrf/wc/document?docname=c02586257&tmp_track_link=ot_faqs/top_issues/en_fi/c02586257/loc:1&cc=fi&dlc=fi&lc=en&product=4221354

I have already changed the PSU and GPU to 550 Ti and Corsair CX500W. So here's some questions I would like to ask.

Here's the stuff I am going to upgrade:
MSI 760GM-P34, Motherboard
AMD FX-8350 Eight-Core CPU
AKASA Venom Power 750 - 750 W PSU

First off, does my current 550 Ti get enough power since my PSU only puts out 500W? If so, would it be so that my system would run better if I only would buy a new PSU, nothing else?

Secondly, if I would buy that stuff, will I be running for example Battlefield 3 on medium graphics with over 60 FPS average?

Thanks for help in advance.

P.S. Does my system have a problem like on its HDD? Because I can barely run BF3 on low graphics and 40 fps average .

Edit: I've been checking this thread twice a day past week hoping that someone would have answered this question. I really want to know will this work

 

[Dilly1O]

Just a sugetions, if you have the money start over. Make a whole new computer if can already updates parts, you will have an easy time doing it. If not, that stuff looks fine, make shure that the ram and cpu have been tested with that motherboard before, even if they have the same socket. Hope I could help

 

[cassu]

Even a little help is appreciated. Thanks

 

[cassu]

I forgot to say that i do have a little delay on controls. Like on Arma 2 sometimes my cursor moves notably later from when I really moved my mouse. Is this because of low quality RAM?