If you want SQM or snort, you will need to go with an x86 mini PC. I like AMD over Intel but that is personal pref. You can get one for well under 500 USD. If you don't need shaping/inspection, I am pretty sure RPi4/5 will do 1G but for the price point, x86 with two NICs on board is better than RPi + USB dongle NIC.
Also mikrotik has din shelf mount options mostly co-relating with PoE, and theoretically all kinds of wall and ceiling mountables should sustain 2-3m fall.
And give 'em toys
Currently the ISP is blaming my Ubiquiti Edgerouter for the poor bandwidth and bufferbloat on the upload on my fibre, and won't investigate until I use their Fritzbox crap.
Pure nat 920Mbps can do pentium m745 from 2004 year with openwrt. I gaved one old checkpoint for free not long ago, dude is happy with it in it's rack cabinet.
GL-inet Flint 2, Turris Omnia, BPI-R3, BPI-R4, all well below your budget ($150).
Possibly "OpenWRT One" as well, it's still WIP.
For $500 I can get or build 10Gbit router (check Deciso devices)