Ahoy there, I've never left a comment before!
Source of Uncertainty - hard to go wrong with this, it adds a lot to the Easel and doesn't have any features you can't use, which is not always the case. Nice to have the sample and hold and slew (integrator) functionality in addition to the noise and quite flexible possibilities of the various random voltages.
Rating: 4/5
SAModular: 140 euro for PCBs + panel or 380 euro for full kit. I can tell you that sourcing each of those 1% resistors is a nightmare, there are so many weird values that are hard to source in small quantities I would be tempted to just get the kit. I have a spare PIC programmed with white noise, just flashed it at Andrew's.
EMS: $149 for PCBs, panel OOS.
Quad Function Generator - No doubt about it that the 208 is missing envelopes. The fact that these have AD/ASD and LFO modes is nice, it takes up a lot of space for four envelopes but there's also CV control over the attack and decay which I think would pair nicely with the SoU. Quadrature mode might be useful in a blue moon, but it's likely it was designed specifically for quad panning. Note that like all of Roman's clones, there are a number of issues with this design, detailed here:
https://modularsynthesis.com/roman/buchla281/281_qfg.htm
Another option would be something based on Aaron Lanterman's adaptation: https://modularsynthesis.com/lanterman/208eg/208eg.htm or taking something from Mutable or 4Ms' PEG and adapting it to 15V. I'd be happy to work on panel stuff if ever that's a concern.
Rating: 3/5
SAModular: 150 euro for PCB + panel. Nothing looks too exotic in the BOM, but I could be wrong since the full kit is quite expensive.
EMS: $130 for PCBs, panel OOS.
Dual Voltage Processor - This is the biggest question mark for me, and I don't see it as very useful given all the hands-on controls on the 208. My recommendation is to sub this out with Model 244 CV Toolbox. You get a dual VCA, quad quantizer, manual triggers, pulse divider, sequential switch and analogue shift register* in 1U. It's a great jack-of-all-trades with no overlap from the 208. There are problems with the ASR, but luckily they have been figured out and there's a well-documented fix here.
https://modularsynthesis.com/roman/buchla244/244cvt.htm - if you like the DVP idea, you could also fit two serge CGS 381 (based on the Serge PRC which inspired Maths) into a 1U Buchla panel - quad voltage processing and only $40 worth of PCBs!
https://www.elby-designs.com/contents/en-us/p560.html
Rating: 1/5
SAModular: 130 euro for PCB + panel.
EMS: PCB for the DVP is $100, panel OOS. For the 244, PCBs are $250 and the panel is $55. It's expensive, but offers a lot more functionality than the DVP, even if you have to throw in a $15 PCB to improve the ASR design.
Touch Sensing Note Memory - Without a Touch Activated Voltage Source this just feels like such a quick victory, and with all the features packed in this is a great fit. I only wish it had 4 more outputs, but no module is perfect. Knowing that the new firmware is going to be ported to the 4U model is just icing on the cake. Don't order one without me ha!
Rating: 5/5
Other (out there) ideas
If you're doing rhythmic stuff and want something cheap and highly effective without the intensity of a 2OC ornament and crime or the 2TT time trigger, there is this: https://modwiggler.com/forum/viewtopic.php?t=247453
Have you considered a Signal Delay Unit? Todd Barton has been posting lots of videos with his lately and it's quite interesting, a different palette than what the Easel typically has.
If you do go with the Quad Function Generator, this has just been announced which would offer a lot of interesting possibilities:
https://1979.ws/dual-sequential-switch/
Lots to think about but that's all for now!