Ok… the amount of available memory might be generally a little bit at the lower end, but shoudn’t cause any problems with the plugins you are using here…
Pianoteq surely is a bit heavier on CPU but an overall CPU usage (in Gig Perfomer) of under 50% shouldn’t cause serious issues.
Maybe you should follow these guidelines for PC-Optimization:
FREE e-book by Deskew - Optimize your Windows PC for the stage! - General discussion about Gig Performer - Gig Performer Community
…hope this helps. 
Oh, and welcome to the Gig Performer family! 