Hi Bloodhound,
I think a laptop will still suit your needs if you want it to be portable in the field. Otherwise a desktop of similare spec would be fine, if you do want a desktop PC then just get a better graphics card the the spec below.
I have a Dell Latitude E6510 with the following spec's:
15.4" Full HD 1920*1080 Screen
NVidia NVS3100M Graphics Card
Intel Core i7 Q840 (@1.87 GHz)
8 GB of DDR3 Ram
256 GB SSD Hard Drive
The usual other bits and pieces that a laptop has.
I got this as I work in IT&T so use it for a wide range of things including image processing and it chunks through data at a massive rate without any hangups
Mind you the total cost with Gold warranty was nearing getting up there, but you get what you pay for.
(Let the Dell haters start to flame LOL).
Cheers
Anthony