Assuming that they are reference cards (standard heatsink, standard clocks, standard amount of RAM), the power consumption should be the same across all brands. Now, this can vary somewhat when it comes to overclocked or non-reference cards, but for a pure, standard, reference card, there should be no difference.
Oh, and what 300W PSU do you have? Not all of them are created equal. The reason some manufacturers increase the requirements is to cover their backsides. A good 300W should power any of those cards, but a bad 400W can have less power available than a good 300W, so they add a significant amount to the requirement just to have some extra margin available.
Lite-on is a good brand, official supplier of HP, it even looks like a quality PSU.
I just bought it and installed it; the EVGA GT 240 Dual Slot DDR3
But pretend that I didn't buy it yet and this is what I would say,
I have a Pentium D 925, and the HP model no is a6021.me (don't laugh at the Pentium) I have 2.5 GB of RAM; I upgraded DDR2 400MHz.
My monitor res is 1680 by 1050, 20 inch dell general purpose monitor.
My CPU is doing a bit of bottlenecking yet I can run Fallout New Vegas on max settings, it set them to max by default and the res to 1280 by 720, I changed the res to 1680x1050 and lowered some settings yet I still consider it max.
I can run HAWX on the absolute highest settings at 1680X1050 with min fps of 20, max fps of 105 and average fps of 42!
I don't think that it's too powerful for my CPU.
Reply as if I hadn't bought it.
Yeah but I have nothing in my wallet, nor allowance...
But, yeah, it works and does fine,
The shop I went to being in the UAE where computer parts are rare and expensive only had the DDR3 version which I got for 340 AED ($92)after my dad bargained with the guy.
I don't think that a Pentium system deserves more money to spend on, I'll just wait till 2015 and get a job land build an 1154 or AM4 build lol