If your Mac or CustoMac is too old to run Sierra here's a low cost option to help you get Sierra on some compatible hardware. Elite 8300 SFF with I3-3220 - 4GB ram- 250 GB HDD - $167 @ Newegg.com (Professionally refurbished) https://www.newegg.com/Product/Product.aspx?Item=N82E16883283859&ignorebbr=1 Evga GT710 LP graphics card $33 shipped AR @ Newegg http://www.newegg.com/Product/Product.aspx?item=N82E16814487221 If you want to run an older version of OS X get the L.P. GT610 graphics card or a low profile 750 Ti GPU. The GT710 doesn't have support in Mavericks, El Capitan or Yosemite. SYBA usb audio adapter $7.49 @Newegg http://www.newegg.com/Product/Product.aspx?Item=N82E16812186035&cm_re=syba_usb_audio-_-12-186-035-_-Product For just $207.49 USD you can get a fully working Sierra system. Install with a Clover UEFI Unibeast Drive. Follow PastryChef's Elite 8300 User Build for the install. This 8300 comes with Windows 10 Pro installed. You can dual boot if you'd like to. If not wipe the existing drive and install macOS Sierra. The Windows 10 Product key is saved in the UEFI if you ever want to reinstall 10. This is not meant to be a gaming or video editing system but if you were to add more ram and a better graphics card you could easily do those two things. This is a budget internet surfing system that performs great with Sierra installed. If you want to go even lower budget you can buy the HP 6300 Pro SFF and use that instead. Currently around $154. https://www.newegg.com/Product/Product.aspx?Item=9SIA5HA55S7807 Enjoy Sierra on your new CustoMac.