When buying a computer for Ubuntu, what should I look for? [duplicate]

When buying a computer for Ubuntu, what should I look for? [duplicate]

This question already has an answer here:
Best hardware for a Ubuntu Computer? [closed] 4 answers
I am buying a computer with the main intent of running Ubuntu, would I get
the best compatibility and performance with a Windows based computer or a
Mac based computer?



If it runs better on Windows based machines:
Which manufacturer (Dell, HP, ...) has the best compatibility with Ubuntu?
Does Ubuntu run on the Intel iX series as well as it does on the AMD series?
Are there any problems running Ubuntu on an AMD processor?



If it runs better on Mac based machines:
Does Ubuntu support Thunderbolt? Will it support Thunderbolt in 13.10?
How good is the support for the hardware peripherals? Network Card,
Graphics Card, ...



General questions about both:
Are SSD's recommended or not recommended? Should you not use a Swap
partition with an SSD?
What is the maximum amount of RAM Ubuntu-64 bit can handle?
Does Ubuntu have support for quad+ core processors?



Edit:
I am interested in getting a Desktop (so if it were a Mac it would be the
iMac). I would want to spend less than $1500 US.