Hey all - Here's what I've ended up with in my Arturia rackbrute case. I have other gear that I use (Digitakt, Waldorf Blofeld, Behringer TD-3, Korg Monolgue) and both a Keystep and Beatstep pro.

current setup

I like the random/generative ability of Marbles and the tonal possibilities from Plaits, Surface, and Chainsaw (and Tides) but wonder whether I should go for more basic oscillators (I also have a Tiptop Z3000 but wish it was smaller)

There's some duplication with the Steppy and Beatstep Pro for sequencing.

As far as my style, I like generative sounds, noise, ambient, but don't mind making straight beats as well (Digitakt probably best for this).

New to modular and hoping for some useful critique where I can add/subtract/substitute for a more useful system. Thanks!

When posting your rack, don't post a JPG pic of it, post a link so people can review your set-up. Just copy the URL when viewing your rack. Like this.
ModularGrid Rack

Pam's New Workout has an optional MIDI expander. If you're working with MIDI hardware, that might be very useful for sync'ing.

Steppy is a gate sequencer. It doesn't output pitch information. You have a Beatstep Pro that offers gate AND pitch CV. What do you intend on doing with the Steppy?

You have the Intellijel Quad VCA. You also have a Doepfer Dual VCA. For the build, I think you would be safe getting rid of the Doepfer.

I like the Batumi and Poti expander. But this is a small case. Is there a dual LFO module to your like that's a lot smaller?

For your ring modular, I would go with Befaco's A*B+C. It's a dual ring modulator but has pots included for level control. That will be extra handy.

Speaking of pots... look up "attenuverter" You need a couple of those to change the polarity of your CV and attenuate it. Befaco also makes a great dual attenuverter.

Your choice of filters are a low-pass filter and a low-pass/band-pass filter. That's a lot of real estate for a small case. Unless there's a specific style of sound you're looking to get from your filters, I'd find a smaller multimode filter.

Do you have a noise source here?

Where are the envelope generators?

If you get rid of some of the fluff you don't need, you can also go with a Disting EX rather than a Mk4. You'll get much more use out of the EX.

You can also save space by purchasing smaller clones of the Mutable Instruments stuff. Again, in a small build, you might want to sacrifice a little convenience to get squeeze in more modules (more functionality).

Thanks for the tip re: posting and for the feedback on the rack. Good points to consider.

A number of the modules I have were deals on eBay (Function, Doepfer VCA, ring mod, Steppy, and both filters) before I had much idea where I wanted to go.

I have been looking at adding an attenuverter and a better filter choice and appreciate the confirmation on where to make changes.

I had thought the tides and function for envelopes but have been looking at something simpler - and agree that smaller LFO would help with space too.

I'll check out the Disting EX and add a noise source - opinions on which modules to check out? I have been leaning toward Doepfer for simplicity and size for EG, noise, LFO...

Doepfer is great. They have a revised line of modules meant to be smaller. A dual LFO and a dual ADSR envelope from them would be just fine.

The A-140-2 for the EG ($168) at 8HP and an Eowave Zone BF ($111) at 5HP look pretty tasty to me. That's an EG and an LFO in the same HP as the Batumi and Poti... at less than the price $350.

As far as a noise source, check around. Noise generators are often paired with sample & hold circuits as well as slew limiters. The ADDAC215 will do all of this in 6HP... and gives you TWO S&H circuits plus two slew limiters.

Doepfer is solid- aside from their crappy MIDI to CV module, their other modules are good and easy to use and affordable for eurorack.