Air-cooling 3950x in 11L case

[dLife_dt]

Hi all! My first pc build and just wanted to pay a bit forward for all the help I've gotten from this community (you are all awesome!!). Getting 4.1Ghz on long all-core loads @76C. Can OC to 4.25 with extra 120mm exhaust fan but its the equivalent of 1/2 more core so didn't bother.

I'm kinda in love with this case+build, which has just 2 potential limitations:
1 - My focus wasn't gaming but rather core count for long simulations and air-cooling (wasn't sold on AIO ease long-term). Lots of great SFF cases+builds for the alternate case of a high-end GPU and smaller CPU, but for this build the next-best case is 18L NR200P.
2 - Lots of unfiltered gaps so regular dusting is a thing.

 

Budget: $1300, plus mid-range GPU tbd
3950x: got new on Ebay for $500
Scythe Fuma 2
ASrock B550m Phantom itx MB
Metalfish S3 case (modded): Ebay seller $130, 3wk shipping time

GPU is the remaining unknown; currently running just a $30 EVGA 8400GS. Planning on rx580 but dunno how much it will mess with CPU thermals when idling at 50C (planning to either game or wk-long all-core simulations, not both). A fun option is a ~230m rx580, move PSU to bottom alongside it, and add 120mm fan (+holes) pulling air from front at the CPU.

 

Thanks for reading! And lmk if you have ideas for a <$3k 128-core PC

 

 

[dLife_dt]

UPDATE:
Got a gtx 1060 6gb 170mm GPU and did some re-arranging + case modding for front ventilation.

 

[dLife_dt]

Noob airflow question: having the case fan pulling in air right up against the grill, I can't feel any flow inside case >2cm away from the fan (at 100%).

 

Adding 1cm space between grill and fan, I feel much more airflow inside 10cm from fan (CPU fans off for testing).

 

Is this an illusion or do grill/fan spacers really help?