Thanks for all the helpful info, I was not aware you could pick up fpga's so cheap... Programming doesn't scare me, I'm used to programming multiwii/arduino type stuff, can't be harder than that ;-) I'll have to plug it into a spreadsheet with the power consumption and see. I had been leaning towards a couple of R290's or R280's in a dedicated rig. I burned out my existing ATI card mining scrypt coins during the mania end of last year. I already have a big external power supply I was using to run block eruptor cubes, which are unprofitable and basically paper weights right now, presumably I could run a handful of fpga's off of it.
Why would blake pools be getting ddos? Seems to be kind of flying under the radar right now, so what's the point of attacking it?
For GPU 7990 probably better $/GH vs 290/280 as its basically same type of architecture (memory speed is not needed for blake its all mostly on GPU core)
290 is about 3.1GH/s
280 is about 2.4GH/s
x versions with more shaders = higher GH/s
7990 is about 5GH/s
for FPGA Lancelot/Icarus are best due to the tri core bitstream I released some time ago
Lancelot/Icarus dual spartan-6 LX150 = 960MH/s ~ 17W each
Ztex 1.15y quad spartan-6 LX150 = 1.6GH/s ~ 35W each
so imho its just easier to setup and get larger hashrate with GPU quickly but you will need cheap electric!, FPGA are a bit hard to get and might take time to setup and acquire a decent hashrate but long term running costs will be lower which is great if your electric is expensive like here in UK
if you got some electronics experience and dont mind programming boards then FPGA might be the way to go, can always ask here for help if you get stuck
worth a note is the Ztex boards send the bitstream to the board from cgminer thus dont need a separate program cable but are harder to find
not sure why people attack the pools maybe trying to exploit or steal from the pools its not that abnormal often get a few attacks per day but its just every few hours atm
most of the attacks are mitigated and pools will 90% of the time auto heal but even so some crashes are not recoverable and needs me to do manual maintenance so if you notice them not working right just let me know
I do appreciate the users reporting issues as I can be quite busy at times
Edit:
looked up the watts used and 7990 looks better
http://www.hwcompare.com/17667/radeon-hd-7990-vs-radeon-r9-280/http://www.hwcompare.com/16198/radeon-hd-7990-vs-radeon-r9-290/but if buying any of these 2nd hand still need to be careful you dont get one thats been hammered by Scrypt mining