HamItUp
I have 4 NESDR mini's + HamItUp upconverter + SDR# (using 4 separate instances) that I use often. Yep, you can run multiple dongles on a single upconverter. 4 at once is PLENTY for me!
I'd recommend adding a HamItUp to your arsenal, as it gives you access below 24 MHz. If you decide to go that route, I'd highly recommend putting it in an enclosure. I sprung for the nice aluminum one they sell.
I compared my setup against my Yaesu FT-840 transceiver. Whatever I heard on the NESDR + HamItUp + SDR#, I was able to hear on the Yaesu. The Yaesu has a better edge with all the internal filtering, but it also cost a lot more than $100
Mick