The only Biostar Tforec6100 754 that I could find is an open box one at New Egg for $25.99 shipped free (New Egg only ships to the US). Just so you know New Egg's open box stuff is OEM and does not come with any retail accessories (although sometimes you get lucky and they send some). The only place I could find a Sempron 2500+ 754 is on eBay. The problem with the Athlon 64 3000+ the previous poster suggested is that it’s a 130nm CPU so it might not be the best choice for Passive cooling. New Egg has an open box Sempron 2800+ for $28.55 ($5.64 shipping), a Sempron 3000+ for $29 shipped, or a Sempron 3100+ for $27.99 shipped. Tiger Direct has a Sempron 2600+ for $27.99 + shipping. I would skip the Semprons all together though and get the Athlon 64 3200+ 2.2GHz Venice 90nm CPU that New Egg has for $36 (you could underclock it). The CPU cooler I would suggest is the Sunbeam CR-SW-K8. I have the Sunbeam cooler on my Sempron 64 2800+ Palermo 90nm CPU and it idles at 18-19C (64.4 - 66.2F). I had it passively cool it and it idled at 30 something Celsius (undervolting would lower the tempatures). I hope that helps you out and here’s all the links for all the stuff I mentioned:
Biostar Tforec6100 754 Open Box OEM ($25.99 shipped)
http://www.newegg.com/Product/Product.a ... 813138268R
Sunbeam CR-SW-K8 Retail ($19.99 + $5.64 shipping)
http://www.newegg.com/Product/Product.a ... 6835207002
CPUs:
Sempron 64 2500+ 1.4GHz Palermo 90nm Retail CPU (bid at $20 + shipping)
http://cgi.ebay.com/AMD-Sempron-2500-So ... dZViewItem
Athlon 64 3200+ 2.2GHz Venice 90nm OEM CPU ($36 shipped)
http://www.newegg.com/Product/Product.a ... 6819103035
Sempron 64 3000+ 1.8GHz Palermo 90nm Retail CPU ($29 shipped)
http://www.newegg.com/Product/Product.a ... 6819104241
Sempron 64 3100+ 1.8GHz Palermo 90nm OEM CPU ($27.99 shipped)
http://www.newegg.com/Product/Product.a ... 6819104236
Sempron 64 2800+ 1.6GHz Palermo 90nm OEM Open Box CPU ($28.55 + $5.64 shipping)
http://www.newegg.com/Product/Product.a ... 819104245R
Sempron 64 2600+ 1.6GHz Palermo 90nm Retail CPU ($27.99 + shipping)
http://www.tigerdirect.com/applications ... No=1530726