My PSU is an old Bestec ATX-300-12E (Rev: A2), originally from an eMachines 6260. According to this topic, my card will run on a 300W PSU. Will mine suffice? I'd rather not have to buy a new PSU in the short term. However, I don't want to risk damaging my hardware. If a new PSU is advisable, can you recommend one that would cope comfortably with future upgrades (quad-core processor, sound card, etc.)?
My motherboard is an ASRock N68C-S UCC; my processor is an AMD Athlon II X2 250 and I have 4GB DDR3 RAM.
normally I would say any mass PC seller's (acer, HP, dell) 300w PSU will run the 5670 as it hardly draws any power but emachines is notorious for using the cheapest PSU possible. I have replaced several emachine PSU after just 1-2 years of operation in basic PCs. You can run the ATI 5670 off that PSU but I would not be shocked if it dies on you within six months. I would definitely be on the look out for an upgrade.
It might run now, but that's not exactly a quality unit so even if it suffices for now it's likely to kill something latter. I've seen those cheap PSUs kill alot of components from running out of spec over a long period of time. If I were you, I'd buy a decent PSU first. At the very least spend $45 on an Antec Earth Watts 380
or the Corsair dirtyferret suggests is sufficient. Honestly though I suggest you get a good quality 500W unit with good reviews (and I don't mean just the user reviews on newegg). Do your research. A quality 500W unit can even power a system with a single power hungry card like a 5870, 6950, or a GTX 560ti. Invest in a good PSU now and you can reuse it for years to come.