Who has a McIntosh C70 anniversary preamp? Thoughts?

I have the C2700. It’s fantastic. I use the built in DAC module and have changed the stock tubes to NOS Mullards and Telefunken. I cannot imagine any reason to ever replace it. 

I've had the C70 for about six months now.  Upgraded the tubes to Gold Lion.  I'm running it with a Benchmark AHB2 amp and DAC3L.  I've had many Mac preamps over the years and all have been very good in their own ways.  The C70 is perfect, the culmination of Mac's pursuit of excellence.  You will not be sorry if this is your choice.

I wonder how C900U compares to more high end tube pres like  ARC Ref 6, ref6SE, VAC renaissance MK V

i don’t know the px of the mac preamps that you’re looking at but the Luxman C-900u preamp has tone controls and will be something you’ll own a very long time. they can be had in the 8-9k range if you’re patient(list 15k). i believe and as do many others that you will find it incomparable.

C 2700 or C 2600 if you want tubes.
C 49 or C 53 if you want solid state. 

+1

Im now favoring the 2700

When I bought my C2500, the only reason I didn't get the C2600 was because It did not have a processor loop which I need.  I am very happy and I am only using the stock tubes.  The DAC module is something I do not use.  You can't go wrong with any of them and it just well be the last preamp you will need.

Yes I did. The BHK blows away the RP5. I'm also considering the c2700 as well. I like the fact the dac module is upgradable and I can make more shelf space (no external dac). I dumped Tidal and only stream Qobuz and my massive ripped CD, DSD and SACD collection. 

There is a thread at Audio Aficionado regarding this preamp.  You also may like to consider the C2500, C2600 and C2700.  All are tube preamps with bass and treble controls.  My C2500 blows away the Rogue RP5 preamp I previously had.  I believe you had a RP5 for a short time as well?