hi
can you report nowadays your ehter hashrate of the old cards like
280x
280
290
380
7970
gtx 970
etc
R9 290 with TheStilt bios, bit over 29 Mhash/sec as of when I last had any on ETH mining (late last week) at 1100/1250. To be picky, 3 in the machine at a total of usually 88.something
I remember my R9 280x cards doing around 14 Mh/s but it's been months since they've been on ETH, they were MUCH better off on ZEC - ballpark 300 sol/s I think, but that was months ago and they've been doing other projects since.
GTX 9xx series - don't bother, they're better off on almost ANYTHING but ETH, even if they are 3GB or higher VRAM cards so they CAN mine ETH at all.
Aim them at something like lbry or lyra2rev2 that older NVidia cards are good at - perhaps even Monero (XMR) and possibly ZEC in a pinch.
HD 7870 was about a 10 Mhash/sec card before the DAG file got too big for it's 2 GB of VRAM. Ballpark 160 sol/sec on ZEC but I don't think I ever got them fully ZEC optimised.