Here are my few cents:
If you want full compatibility with best featureset under free license then
stick to Intel. In general Intel will be quite pricy compared to AMD CPUs.
Despite the big "stinko" master Torvalds has sent towards NVidia, they still
provide the best 3D performance, most stable driver set and best Video
acceleration under Linux if you use their propritary driver, which is of
course a no-no under Trisquel. By using Noveau they still will perform great
and can easily beat the fastest Intel stuff available. If you dig a bit in
the forum / mailing list you will find a few postings of me where my old AMD
dualcore (2x2.7 GHz) with GeForce 9800GT could still compete under Xonotic
with the fastest Intel CPU plus fastest onboard graphic adapter. I can
through together a system like mine with a fast used NVidia GPU from the bay
plus silent GPU cooler for below 300€ while the Intel opponent (Intel i7
3770K) plus motherboard costs > 450€.
You be the judge !
Noveau has its issues though like lack of power management (e.g. fast
spinning fans, higher power consumption) which you can compensate by choosing
a low-power AMD CPU and simply applying a silent cooling solution to your
NVidia GPU.
If you want issue-free 1080p playback you should either get an Intel-based
system or simply use an NVidia adapter with a fast enough CPU (> 2-4x2.7
GHz).
While AMD cards are a big no-no under Trisquel as well because of their ucode
required to run the free radeon driver, they provide a better 3D feature set
compared to Nouveau but not as good as Intel.
