I purchased a mining machine about 2 weeks ago with a friend of mine, right before the sapphire 5830's went out of stock. Nothing has been overclocked, and we have run the machine for only about a week and a half so far with no issues, well other than difficulty going up. Here are the parts:
1xMSI 890FXA-GD70 AM3 AMD 890FX SATA 6Gb/s USB 3.0 ATX AMD Motherboardhttp://www.newegg.com/Product/Product.aspx?Item=N82E16813130274
1xAMD Sempron 140 Sargas 2.7GHz 1MB L2 Cache Socket AM3 45W Single-Core Processor http://www.newegg.com/Product/Product.aspx?Item=N82E16819103698
2xSAPPHIRE 100297L Radeon HD 5830 1GB 256-bit http://www.newegg.com/Product/Product.aspx?Item=N82E16814102878
1xCORSAIR Professional Series Gold AX1200 (CMPSU-1200AX) 1200W ATX12Vhttp://www.newegg.com/Product/Product.aspx?Item=N82E16817139014
2xKingston 1GB 240-Pin DDR3 SDRAM DDR3 1066 http://www.newegg.com/Product/Product.aspx?Item=N82E16820134489
1xWestern Digital Caviar WD800BB 80GB 7200 RPM 2MB Cache IDE Ultra ATA100http://www.newegg.com/Product/Product.aspx?Item=N82E16822136292
The case is an old ATX tower I had, will throw it in if you are interested in entire system, has removable motherboard tray, tool-less entry, front and rear 80mm fans. Stock speeds range about 450 to 500MH, have not tried overclocking. Was built with expansion in mind as there is room on the motherboard(without risers) and in the case for 2 more cards, and the powersupply should be beefy enough to provide the juice. The powersupply is awesome btw, nicest I've ever used. Motherboard isn't too shabby either, has power/reset switches on board, dual NIC's, and 5xPCIE slots(4 use-able with no risers).
Looking for $800 shipped(negotiable) for the whole system(good deal with cards), but can sell in parts. I am accepting payment through dwolla or paypal. I have an ebay account with good ratings. Please PM me with offers or questions. Located in Orlando Florida, near UCF if interested in pickup.