Centralized resource for benchmarks?
I can't seem to find any centralized database for the various attack modes + GPU/CPUs hash rates. 
I've found a couple benchmarks for specific devices: is there anywhere these are being aggregated?
There's no such thing. I think it's too complex if you take the entire bandwidth of attacks combined with different drivers, versions and GPUs into account. I think the Phoronix Website has some automated benchmarks for a reduced set of raw hashes, so that's a good indicator.
Github has a lot of benchmark information for different GPUs.
From there you can make a small Excel sheet with the relevant GPUs for you.