Intel I5 2400 Processor
Asus P8H61-M LE/CSM Motherboard
Sea-gate Barracuda 500gb 7200 Rpm
Asus Radeon HD 7750 1gb
AMD MEMORY Entertainment Edition 4GB
Silencer Mk III 500W Power Supply
Total Cost 572.94
If gaming is your primary concern, and your budget is limited, you'd be better off going cheaper on the CPU and heavier on the video card, a 7750 is not a particularly powerful graphics card, and for gaming, graphics is where it really counts.
Although, I do have a build saved I use when people ask for advice thats in that price range. It utilizes a cheaper Phenom II processor and a much stronger graphics card. The i5-2400 is a stronger processor, however it really wont "shine" in gaming paired with a weak graphics card.
It'll work yes, but the 550 TI is not a particularly strong video card, you could do much better for not a whole lot more in a 6850 or a 6870, even an older GTX 460 is a stronger card than a 550 TI. Take it from someone who owns one. If gaming is your primary concern, you'd be better off dropping to an AMD Phenom II and going heavier on the video card maybe even a 7850.
As far as the PSU.. Its not the best choice in that budget range no:
How about an i5-2300? Not a whole lot cheaper than a 2400, but if you're trying to cut corners, in a gaming rig the video card matters more than the CPU. Although in 2012, I Wouldn't recommend a dual core (which means i3s)
Out of curiosity, why are you afraid of overclocking? And whats wrong with Newegg? I've ordered from them many times, their shipping is fast, I've dealt with their customer support on returns, they're great.
BTW, my 550 TI is a Zotac AMP edition, it was 170 bucks, The AMP editions means its overclocked, in this case about 100mhz over, sadly I bought it on the recommendation of someone else, I have since learned that for that same price I could have gotten a stock 6870 that would outperfom it.