ARM device from China will be cheaper, smaller,more power efficient and will run Ubuntu just as fine.
> 2.8Ghz P4 or better CPU (pentium 4 is very very green)
> 80GB SATA HD (spin it yeah, Ubuntu comfortably fits to 5GB)
> VGA port ???
The warning has been going out for quite some time:
http://www.thinkoutsidetheslide.com/issue287may282013
You're wasting your money if you buy a PC with a VGA port and no HDMI port.
VGA will stop being used when it stops fitting most use cases out there, and not before. The connector standard is capable of 2048x1536 at 85hz, which, making an educated guess here, is probably a higher resolution than the monitor you're using right now. Most monitors and TV's sold nowadays are 1920x1080.
4K will probably be what finally kills it off (3840 x 2160), but I'd give that another 2-5 years before the hardware reaches enough market penetration for manufacturers to stop including the plug out of necessity.
Yes, VGA still has to be used for devices that only accept VGA (like a lot of projectors, very few of which can handle those specs), but apart from that, it should be avoided because the image quality is just that bad.
The displays are identically sharp and colorful. Nobody would be able to tell you which is connected over which interface.