i looking for a cheap AMD processor that is better than my current 4-year old Pentium D 2.8Ghz processor. I wont play any games on it as I have my Xbox 360 for that purpose. I just want to see HD content without the need for any graphics card.
If you live in the usa, check craigslist for a sempron 140 am3 that can run with either ddr2 or ddr3, depending on the motherboard chipset. New they go from $33-37 at places like newegg. I'm trading for one with a guy on anandtech's for sale forum, downgrading my cpu. Another gentlemen has a 2300be 45w dual core with board for $65. It will run routine tasks ok. For blueray playback, look for a motherboard with 785 chipset and hdmi port; they can be selected to use ddr2 or ddr3, but not both, so choose carefully. Newegg had an msi 785 ddr3 board for only $49.99 with email promo code recently. If you must buy ram, get a 2x2gb ddr3 kit for around $100. Newegg had an open box regor 245 cpu for around $45 shipped recently; I am trading my regor 250 for the sempron and some cash. I live near frys, so I'm spoiled.
Right now newegg has a 95w kuma 7850 black oem cpu with biostar 770e atx board for $79.99 before $10 rebate. It doesn't come with a heatsink. This board uses ddr2. I have seen 4 gb kits of ddr2 or ddr3 for around $60 recently on my local craigslist. Some are unopened.
If you can afford it, like Simon Says, the Athlon IIx3 is the best buy. The x4 is also a good deal. The x2 isn't as great bang/buck but is still good. The sempron is simply the cheapest. All cost between $40-100. You don't need to spend anything more than that.
And if you can find some older CPUs like the 7850 BE or an old phenom x4 (an xx50 model only, you want to avoid the TLB bug)
They match up well enough that you can compare them to the Athlon II based on their clockspeed and number or cores.