pre-amp for original Marantz Model 9 mono amps?

What pre-amp would you mate with a pair of museum quality pair of original unmodified Marantz Model 9 mono amps? Also available is a pair of Marantz Model 8 mono amps for rear channels for a home theatre setup although assume a two channel setup is the objective here.
I used Marantz 9 amplifiers for 20+ years and was very pleased with the match of a Conrad-Johnson PV-9 over the last 10 years I lived with these wonderful creatures. Today, I would be very inclined to consider combining these amplifiers with Aesthetix tube gear: Calypso line stage (and Rhea phono stage, if you're also into vinyl), or Janus full function preamp. The Aesthetix gear will give you all the functionality you could look for in a modern control center preamp, plus it will complement well what you like about the Marantz 9s while providing them with a more sonically neutral partner.
Courios to see why you are not considering the Marantz 7 (tubed) preamp?

To anser one question, I already own a Marantz Model 7. I wanted to generate a discussion that might consider new as well as old products. For exapmle would one be wise to try a Conrad Joanson ART or ART II, or if really rich an ACT II or the Boulder elite products? Would the amps capture the nuances of current products? Thanks to the responders! I hope that one day TAS would compare the Model 9 amps to the Tenors, Halcro's Edge etc. to see if we have really made progress (I can't afford to purchase all of these goodies, and not too many other people could either!)
Tubeperson, I'll offer a perspective on your last question based on my experience as a previous long term owner of Marantz 9s (20+ years).

As much as I loved those amplifiers (particularly when run in triode), imo, they can be competitive with the best designs of today only with parts upgrades; in purely stock parts condition, the increased quality of capacitors, resistors and other components available today simply move current high-end tube equipment past these classic beauties. Of course, doing any parts upgrades would materially reduce the value of a "museum quality" pair. In my case, I made a choice to upgrade a number of critical capacitors and resistors, and to bypass the bass filter and volume control (no circuit change, just parts upgrade as Saul Marantz might have done himself were the parts available to him). There was a material increase in resolution and transparency with those modifications.

But even with those modifications, I've found several contemporary amplifiers to be more truthful in their musical accuracy than my long cherished Marantz 9 amps. For example, the current Conrad Johnson Premier 140 or the older Premier 11XS (using EL34s in triode). And, for my musical priorities, I find my current pair of Atma-Sphere MA-2 OTLs better suit my needs in terms of neutrality, speed, resolution, dynamic contrasts, and extension at both the top and bottom of the frequency range. For my listening priorities, I simply could not return to the Marantz 9s as my primary amplifier, much as I value and admire it.

But, a classic pair of Marantz 9s are amplifiers to be cherished. With excellent, well selected vintage tubes, they still will charm the socks off most other amplifiers and they are beautiful to listen with. I do think they are well worth pairing with some of the best tube preamps available today, because the best preamplification will still improve what your Marantz 9s are able to deliver. Best wishes in your continuing enjoyment of these classic treasures.
What do you audiophiles think about mating the Marantz 9s with the solid state classic JBL SG520 (graphic controller) preamp?