What preamp with both line stage and phono?

Understanding that the recommendations here are primarily tube preamps, let me throw a solid-state preamp into the considerations. The Mola Mola Makua preamp comes highly recommended and especially because it can be had with a world class phono stage.  It's the same circuit at the highly regarded Lupe phono stage. The phono stage is remarkable! And the preamp can also be fitted with a world class DAC (same as the well-known Tambaqui) if digital is part of the mix.

In terms of output impedance vs. input impedance keep in mind the general recommendation:  The input impedance for an amplifier should be 10 times the output impedance of the preamp.  

Looking for something Nelson Pass related?  How about the old Threshold FET 9e (if you can find one)?

+2 on the VAC recommendations. The upper models (with 12 db gain) all have essentially the same phono circuit (6 x 12ax7, transformer coupled with top Lundahls), albeit with varying refinements in execution. They are genuinely excellent phono stages. For the past 12 years I’ve run a Phi Beta preamp with MC/MC. Predecessor to the 2A Signature Mkii, which has a variable loading impedance dial and other improvements, the Phi Beta is fixed at 470k. So I had VAC modify it with internal screw collars that let me slide in any resistor values I choose. I use nude Vishays. This phono stands shoulder to shoulder with my Allnic H3000mkii and actually bests it in some ways. It is not a compromise. I have no doubt the more recent models like the 2A Sig are as good or better, and may be found used for near your budget if you stretch it a bit. Build quality is superb: they last and last.

I read your post several times, I am confused if you are actually looking to upgrade the pre-amp, or if you should be trying to upgrade your amplifier?

you love the Shindo, so try a different amp.

Try a Coda 16- my 15.5+ sounds exceptional with my 3.6r’s. 100 watts per channel of class A, then it transitions into class AB 150 wpc, 100 amps of current your maggies will appreciate, and it doesn’t get hot. Have not heard their 07x preamp, but have read that it is warm as tubes, and obviously matches well with their amplifiers.

The coda 16 has 50k unbalanced input impedance, but as suggested above maybe you are in the market for a dedicated phone stage? 

that may satisfy your "curiousity".

Have you ever heard if it isn't broken don't fix it.... If you just have to audition several VAC preamps.

I went to my Monbrisson from a Jadis JP200. I would not consider any other preamp to be, overall, an upgrade over the Shindo, but my suggestions if you want to try something different but keep something like the Shindo sound would be a used VAC or a Jadis JP80, my experience with them has been that they have that midrange that you like.  Don't know anything about their output impedances, though.

If I were looking to upgrade, I'd strongly consider a preowned Conrad-Johnson ACT2. In my opinion, and just my opinion, one of the finest preamps available at any price.

https://www.stereophile.com/tubepreamps/305cj/index.html
https://www.stereotimes.com/post/conrad-johnson-act2-series-2-preamplifier/

@soix 

Good advice.

I would just add that at your budget level you’re likely better off with a separate phono pre as it will likely surpass most if not all the ones included with a preamp.  It also gives you more flexibility to choose one that best matches your sonic preferences rather than just taking whatever comes with the preamp.   Just my $0.02 FWIW. 

Crimson 710 !!

The VTL 5.5i is hard to beat.

Just about any phonolinestage, other than those Shindo units, ought to have an output impedance far lower than 5000 ohms, which is quite high.  In addition, you might consult with the manufacturer(s) of an amplifier with an input Z of less than 50K ohms, to see whether they can permit modification of the input stage to increase input Z.  Usually it only requires changing a single resistor, if the circuit permits.

If I had the (your) older MM/MC version I would want to try the later (MM only) version of the Monbrison.

Forget who reviewed it, but the gist was that it was similar with extended info @ high/low frequency extremes.

DeKay

Can't go wrong with the Atma-sphere MP-3. With all due respect to the other excellent product out there, I don't believe you can beat it for the dosh. Phono stage top flight, BTW. It is also fully differentially balanced. I own a fully updated MP-1 and I continue to be amazed how close my friend's MP-3 gets to that standard. Good luck with the search.

OP, consider the  CAT SL1 preamp with the built in phono stage. The latest versions are the best tube based preamps on the market, IMO.

I am using the Spatial Audio Raven preamp with a Pass Labs X-350.5 amp and it is an excellent pairing.  While I love the Pass amp it is a beast and too big for me to be moving around at my age so will probably change amps and thinking of going back to tubes. The Raven/Pass combination with your Maggies should be magical.

Used VAC Signature Mk IIa SE if budget allows.  

I’d recommend the new Spatial Audio Raven or Aric Audio Motherload XL preamps as both are outstanding and offer trial periods so little/no risk.  Pair either with this used Herron phono pre and you’d have one helluva setup.  Both preamps have an output impedance of around 300 Ohms so no problem whatsoever with your Pass amp.  Just some ideas, and best of luck. 

https://tmraudio.com/vinyl/phono-preamps/herron-audio-vtph-2-tube-mm-mc-phono-preamplifier/