Need advice from OTL experts

I have recently purchased a used pair Transcendent T8 OTL mono blocks (80 watts into 8 ohms) for my Quad 63 ESL speakers. For many years before this purchase, I have used ARC Classic 30, Classic 60, D115 and ASL Explorer 805 SET mono blocks with the Quad 63. I am a strictly vinyl person and my preamp is the ARC SP8 with a VDH Frog HO MC cartridge on a Oracle premier II TT. My speaker cable is MIT MH 750 extended, VPI phono cable and Cardas Decade interconnect from Pream to amps. The bottom line is I have never heard better sound and music coming out of these Quads before the OTL's and I am very pleased with this amp and speaker combination. The sound very pure, clean and precise without the typical tube coloration and faster than all the amps I had before. The gentleman whom I bought the OTL's from told me my SP8 preamp's output impedance at 1000 ohms is too high for these amps and speakers. I have owned this SP8 for many years because I love its phono section and I hate to part with it. My question is if this is a true statement with science behind it and if I would benefit from switching to a preamp with lower output impedance. I have looked at Transcendent web site. Their preamp has output impedance of 200 ohms and some other preamp brands have as high as 2000 ohms. Many thanks in advance.