$1500 for storage(SSDs)- what would you do?

[F.E.A.R.]

1500$ ? yeh ill be going for new ~6x slc ssd soon

f.e.a.r itll put your ramdrive to shame

But only for 2GB, than your cache is full of data.
Let a Flash-SSD-Array run with many simultanious accesses and can see a big dropdown.
No Flash-SSD can beat the raw performance of DRAM-based SSDs (since 30 years)

See Ramsan 440 or Violin 1010

Forget mentioning everything unrelated to Raid Card cache. Can you simply advise how cache on the raid card will be improving read speed?
Does the OS read from the drive or the cache?

When you start a second run of a app (or whatever), you can read from the controller-cache. Max. 1600MB/s. is no problem for one controller.