for me its either 7870/270X or 7950/7970/280/280X, got some off ebay for 40 and 60€, same idea here though i will re-purpose my existing nvidia rigs for these cards once i sold them (completely)
I dunno. Far as XMR is concerned, my feeling so far is Gen1 is Gen1. Got a rig with 4x7850 hasing 1.2kh/s drawing like 430 watts or so. Any combo of three 7950/R200 is about the same.
I get the feeling mining XMR is all about giving the compute unit good access to good memory with good timing. According to the bitcoin wiki, cryptonight was originally a CPU protocol, and the defense against ASICS is dependency on rapid access to an amount of L3 cache that isn't practical for an ASIC. GPU mining then is a handicap, the memory is slower and the compute units can't get at it as quickly. Going from 7850 to R9280 makes more noise but I don't see that it's doing any more work. Granted, the 7850's have decent RAM, and elpida ram seems like it comes timed right from the factory most of the time. And the 200's are spectacularly crappy in the memory quality department. Boils down to paying more money for lousier RAM, basically.
But going from a 280 to a 290 -- lousy RAM and all -- now we're talking whole nother ballgame. My 290x smokes everything in my collection, including my 470's. AMD said they were giving the compute units better access to memory, and they delivered imo.
Only reason my Gen1 200's haven't been drop-kicked into the woods is because they hash Pascal like it's going out of style. Still trying to wrap my head around that one (I mean, my kid is a senior math major, I'm like when and at what cost are they gonna start teaching you cryptography already) but I think it's one of those ethereum things, where the total amount of RAM at your disposal is a big factor.
Only reason I haven't crowned the 290 the el cheapo king is there's too many plugs on it, and I can't figure out how to hook em up to my el cheapo HP server PSU's. Also it's hard to cram it into a milk crate.
Interesting stuff in the database. Interesting lack of correlation between specs, price and hashrate. Also interesting to see what the fancy CPU's are up to. A Dell workstation motherboard with five PCIe slots, two E5 processors, ram and heatsinks is about $400, about what the windows folks pay for a new mb with one chip. Wonder if that kind of hybrid is the way to go. I'd gain about as much as adding another graphics card, albeit at a cost of probably 300w. If I could undervolt that sucka....I dunno. Might be worth doing just to say I did it. I could put a rack of 290's on there and blow the transformer. That would be cool.