Do you need to use ALL balanced cables?

I have: XA7ES CD Player: w/balanced & unbalanced outputs GFP-750 Preamp: "" SF SFM-160 Amps: unbalanced only (feeding Virgos) I have decided I like the sound of the passive preamp verses the cd player's variable analog outputs. I am currently using unbalanced interconnects between the CD Player and the Preamp. Will I see improvement if I spring for a set of balanced cables to connect the Cd and preamp?
Addenum: I am 2 Meter Nordost Red Dawn speaker cables, and a 2 meter interconnect between the preamp and the monoblocks. The CD to preamp is an old Esoteric Audio cable that I bought new for $70 ten years ago. The sound is excellent as it is. The Nordost cabling improved my system noticeably.
No definitive answer; won't know unless you try. I have one of the predecessors to your CD, the 707ES, and I favor the balanced over the single ended outputs. Any audio dealer worth buying from should loan you interconnects for an at home trail.
I think you'll hear improvement even with a short run. Some balanced interconnects make more difference than other ones, like MIT or Synergistic Research.
You may be able to lower your noise floor slightly with the use of the balanced cables. The balanced cables are especially great for longer runs. If you used identical balanced and unbalanced cables side by side from the same manufacturer, I doubt you could tell the difference. However, if your run were greater then 1 meter than the balanced cables would make a difference.