Advice. What brand desktop?

Depends what your plans are if you is it for surfing the net and basic spreadsheets check dell's website.
Everyday they have a "deal of the day" You can pick up a decent desk top for $399 nicely equipped.
As for Mac they are nice but a little overpriced in my opinion then when you run Windows on a mac you dont benefit from the best part of a mac.
The best thing is you can not get virous's on a mac.
I use both,and am responsible for keeping several computers working for work and at home.
If you want a simple easy to use PC I would recomend a Mac.
Also the digital photo software on apple is very nice.