How viable are these cards?

I've accumulated quite the collection of hardware from a relative that has done a lot of mining for various coins. its mostly been multi processor server boards and tons and tons of ram but lately i've gotten quite the stack of cards and older high end systems.
the systems are first gen i7s with fancy bits in them.
the cards are where its at and I was wondering if I am letting good cards go to waste.

so far I have that I am unsure about:
2 Geforce 560Ti in sli on a i7 960
1 Geforce 660Ti with another i7 (unsure of specific model)
1 Geforce 750Ti (working pull, donated rest of system to a family, with another card in it)
2 R9 270 on dual opteron DDR2 era server board

I know the R9's are atleast ok since I have a 270x and a 7870 in my main system and they are similar.

should I be doing something with these or are they worth my time?

Viability would clearly depend on their intended use which is not memtioned. It's also in the eye of the beholder. Those may be upgrades for someone, ha know?

What are you really asking... ?

I agree, more information about intended usage is needed to determine their viability.

all usable, check!
all playable, check!
all saleable, check!
all viable, check!

The 750ti is a really nice card for HTPC builds. I have a non ti, and it's plenty enough. light to medium gaming, streaming with ease.... it's a nice little card. Can use for Dedicated Physx as well.