I must have assembled some 30 PC over the years. In recent years every one works with Linux. Intel, AMD, single core, Core 2 Duo, Quad core, Phenom and the latest i7. It never cross my mind that I could not fit a Linux to it. Newer Linux is now superior to MS Windows. For my latest Intel i7 rig Vista works but needs some drivers. For Linux I never bother with drivers.
Open Source computing has always been there once Microsoft published its inner work for the first generation of 8086/8088 machine.
Having said the above there are always problems if you go for the latest technology before the open source developers have a chance to develop the software or the drivers. Buying branded names is possibly the worst way to get it work on open source operating systems because the manufacturers tend to cut corner on the hardware to cut down the cost and these hardware may need specific drivers.
Open source OSes like Linux and BSD systems survive mainly by generic drivers.
If one has an interest in Linux then a motherboard with at least one IDE channel would be recommended as many current distros have been written to search a CDrom from the IDE bus and may not be able to recognise a CDrom hooked by a Sata connection.
I suppose any new PC that has been preloaded with a Linux is supposed to be open sourec friendly but I have not bought one myself to try it out.