I just gave the data sheet for the 23A256 a quick look over.
It seems that you can send a control byte or two to set the address etc. and put it into sequential mode. Thereafter every 8 clock pulses stores a byte until you stop.
You're right about the FIFO though, it's probably a better choice. At 50MHz you don't need all that shift reg stuff in the design on the other thread I would think, just use it as a 9-ch analyser.
I just had a look at the price for an IDT7208, $30-40, yikes! Still you only need one. The 23A256 is $2 and for the same bit width you need 9 of them, OTOH 4 bits is probably enough.
Rob