My budget has been really low the last few years. Planning for the future, I’ve picked up:

Focusrite Saffire Pro 40 (the 18i20 may be fine for you), Presonus Digimax FS via ADAT, 2xBehinger Px3000 patchbays, Emagic Unitor8 MkII and MkI midi patchbays. Probably around $1000 total, since the Pro 40 was new, but lots of room to grow with. If I run out of space, it’s a matter of more inexpensive patchbays that I can easily justify.