Which sub should I get for kh120 monitors?

Hey guys, I'm trying to figure out which sub would make more sense in my situation right now.

I have Neumann's kh120 that I actually really like, but I do plan to upgrade it for ATC 25s or 45s sometime down the road, but it might take a while to get the funds for it.

Will the ATC SCS70 make sense in my situation? will it work good with my kh120s until I get the ATCs? or should I just get the kh750 for the meantime and then just get the ATCs whenever?

The one thing I don't like about the Neumann sub is the DSP.. I just want to stay analog. I should mention that I have a very good treated room.

Thanks!