Hey man! I have a decent Pc I thought but I still get a bit of lag on Hexxit :/
16 GB Ram
Nvidia GTX 660 Ti
Windows 8
64 Bit
I get about 50-80 fps when recording with xsplit...or I did. I altered the settings in the technic launcher after so that Technic used up 4 Gb of my 16 Gb ram. I am hoping it helps with the lag a bit, I will find out my next recording session!
See for yourself what the quality is like: http://www.youtube.com/watch?v=OpDGAKWWnYs