Significantly improved GPA. Should I leave it here or continue improving it?

[dmacfour]

My B.S. and M.S. GPAs were 3.1 and 3.4 respectively.

I needed to get some science/math/engineer prereqs out of the way for PhD programs I want to apply to, so I took the opportunity to kill two birds with one stone and improve my GPA.It's been about a year and my GPA at this institution is 3.75. My background is psychology and I'm looking at engineering programs that admit non-engineer applicants. Most of the schools in question are R1.

 

All other things being equal (GRE, GPA, research, letters, etc), is this a sufficient improvement? Is there any reason I should take more classes to improve on this GPA?