sapb, which card (est)

I am doing some tests using sap codvn b (bcode) (-m 7700) and using below cards (test in w7-x64, 1 hash loaded):
Device #1: Tahiti, 3072MB, 1050Mhz, 32MCU (=HD 7970 vapor)
Device #2: Hawaii, 3072MB, 1040Mhz, 44MCU (=290X)
Speed.GPU.#1...: 236.2 kH/s
Speed.GPU.#2...: 322.8 kH/s

Device #1: GeForce GTX 660 Ti, 2048MB, 1137Mhz, 7MCU
Device #2: GeForce GTX 260, 896MB, 1242Mhz, 27MCU
Speed.GPU.#1...: 60328 H/s
Speed.GPU.#2...: 25616 H/s

Now I've added an Asus HD 6990 which only does:

Device #1: Cayman, 2048MB, 830Mhz, 24MCU
Device #2: Cayman, 2048MB, 830Mhz, 24MCU
Speed.GPU.#1...: 37173 H/s
Speed.GPU.#2...: 37182 H/s

Looking at http://golubev.com/gpuest.htm I would have expected that the HD 6990 would be close to 290X however it is lagging behind. Probably something to do with algorithm because MD5 is doing:

Device #1: Cayman, 2048MB, 830Mhz, 24MCU
Device #2: Cayman, 2048MB, 830Mhz, 24MCU
Device #3: Hawaii, 3072MB, 1040Mhz, 44MCU
Speed.GPU.#1.: 5264.3 MH/s
Speed.GPU.#2.: 5267.3 MH/s
Speed.GPU.#3.: 12174.7 MH/s

What would be the best method to estimate the performance on sap codvn b algorithm to try yet another card (2nd hand)?