Like the Zoom H6?
As far as pre-amps go....you are saying 701d, Zoom use about the same pre-amps. Would 680mkii be in the same ballpark? Does anything in the sub-$500 blow those pre-amps out of the water? (I will look into the first gen MixPre's)
NO... F6 or F8n are about the same as NEW gen Trashcan, I mean Tascam (701d/680mkii)
the older Zoom had issues with overloading the input stage
I did not like the limiters on the 701d, and have not used an 8n personally, but have heard good things about them
the Sound Devices are Class A preamps, but I didn't like the limiters on the MixPre gen i either compared to my USBPre2 or old 702t
that's why I went with MixPre gen ii that utilizes 32bit Float and NO LIMITERS
if you record orchestras you might like the ability to not have to ride your levels thru dynamic transitions
otherwise you will need to spend some $$$ on a proline Sound Devices (664/688/833/888/Scorpio) to get better preamps and limiters for 24bit