Tvheadend

I'd like to know if anyone has any rough idea what the system requirements for timeshifting of HDTV are? my system is rather weak but it manages to play everything i threw at it so far flawlessly.
my system:
Operating system: Ubuntu Linux 12.04.1
Kernel: Linux 3.2.0-38-generic-pae on i686
Processor: AMD E-450 APU with Radeon(tm) HD 6320 Graphics, 2 cores
RAM: 2GB DDR3
TVheadend Build: 3.5.64~g5e79502 (16.03.2013)

the thing is with my system, sd channels work just fine - a bit buggy but that is to be expected with the nightly builds, but most of my channels are HDTV so i'd like to know if anyone has experience with timeshifting HDTV and could give me some advice on a more sufficient hardware config. i could e.g. easily add more ram or switch to a ssd drive for the timeshifting.

regards,
uuzi