Accuphase single-ended vs balanced with P-1000 and C-275V

[Breakdown7]

When using my Accuphase P-1000 amp with C-275V preamp, I've always questioned whether or not to use balanced vs. single ended cables. To my understanding, neither the P-1000 or C-275V are truly balanced designs. (someone correct me if I'm mistaken). With this in mind, it seems using RCA cables would make for the most direct signal path and better sound quality. Curious as to you guy's thoughts before I invest in more cables.

None of my sources are Accuphase, so they are the standard XLR pinout design used with gear here in USA. I currently have been using balanced cables throughtout and select "invert phase" on the preamp. Maybe going to nice single ended cables throughout would be the better option?