Good morning,
I am just a beginner piano player but I use Pianoteq 5 with a repurposed netbook (Asus EEE 1005 PE, 2 GB Ram); I use an external USB audio interface, a Matrix Audio M-Stage HPA-2.
I use standard lubuntu 14.10 with the latest low-latency kernel (3.18.1) and I have followed linux audio tutorial in order to improve the netbook performance (following it gives you a major improvement, it is key to follows it); in addition I have disabled some processes at startup such as CUP
http://wiki.linuxaudio.org/wiki/system_configuration
please note that I had to adapt the tutorial when it cames to CPU frequency scaling; I didn't compile any kernel
I don't use Jack but alsa, jack is a bit power intensive and decrease netbook performance, I use the netbook just to excercise but a friend, a piano teacher, tried it without any issue
With Blutner addon, sample rate 48.000, audio buffer 128 samples and ALSA I obtain 2.9 ms latency
I set the system to autostart pianoteq at full screen, full screen save some processing power