Unless E-Bay seller made mistake explaining specifications, this card most likely a fake. GPUGRID forum post somewhere mentions GTX650 purchased on E-Bay for GPUGRID crunching being a G92 core card.
GeForce GK110 Boards are 3GB or 6GB while Tesla GK110 are-(5GB:k20m/6GB:k20mx/12GB:k6000)- no GK110 2GB exists. GTX 780 has 6GB card made by eVGA,MSI,Asus. Titan(black) have 6GB. GTX 780ti is 3GB only. All GK110 Contain GDDR5 memory, only low powered Kelper (GK208/GK107) have GDDR3 circuitry.
If price of GK110 boards go down-- pick one up or wait until Maxwell GM204 cards are released by early October.
A GTX 880 board build--16 SMM/64 core blocks, 64 warp schedulers, 128 dispatch units, 64 instruction buffers, 2048 total cores(1024integer)128TMU/32?ROP?/256bit memory bus rated for 170watts similar to GTX 680. 4GB GDDR5 memory on reference models, maybe 8GB on custom partner boards .
Maxwell SMM contains 128 total cores, 64 integer, 32 load/store, 32SFU,  64bit conversions,  8/16/32bit conversions, 4 warp schedulers, 8 dispatch units, 4 instruction buffers, 4DP cores-one in each 32 core block. SMM contains  32 core blocks.
A GTX870 (150?watt) has 13SMM/52 core blocks equaling 1664 cores, 128TMU, 32ROP/256bit memory bus amounting to 3600~ FLOPS.
Maxwell GPC contains 4 SMM totaling 512coreinteger, 32TMU, 16ROP. Kelper GPC is 3 SMX totaling 576cores(96 integer)48TMU,16ROPS.
Maxwell Performance running GPU-GRID ACEMD is more efficient compared to Kelper. A GTX750ti (60watts) with 640 cores/40TMU/16ROP/128bit memory bus is ~7% slower compared to a [140 watt] 960 Kelper core/80TMU/24/192bit bus. GTX 750ti is 7%~ faster compared to a [110/130watt] 768Kelper core/64TMU/16or24ROP/128/192bit memory bus.
Considering all factors: a 2048 core Maxwell will have higher FLOPS compared to reference 225 watt, 2304 core GTX 780 rated at ~4000 FLOPS due higher reference clock speed. GTX 780 running 1GHZ pushes out 4608FLOPS. Maxwell and Kelper are dual issue. Maxwell cards are able to run higher speeds enabling boost clocks Kelper can only dream of reaching for weeks on end. Maxwell's Improvements show GTX 750ti to be best performance/watt ratio card for GPUGRID computing. A GTX 660ti running at 100 watts (1.000v) is second, along with GTX 780.
A GTX 870 [150TDP] could perform similar to 780 [225TDP] running ACEMD unless GTX 870 128TMU calculations synthesis not on par with GTX 780 utilizing 192TMU. Figuring GTX 880 performance to a Titan due lack of TMU will be shown by current complex models. ACEMD code give's TMU a work out.
GM204 is NOT a replacement for GK110 cards. It replaces GK104 stack. GM204 DP performance will be similar to GK104, if not slightly better due higher clocks. GK110 64DP core SMX positions Titan series to be rivaled by AMD Tahiti stack for DP64 compute. AMD Hawaii 290 series runs at 1/8 of single and 1/2 for Firepro series, expect this server grade card completes against Tesla cards rather Titan due lack off ECC and hyper Q along few other Tesla features(12GB of memory.)
Maxwell mobile flagship GTX 980m could be a GTX 870 with lower clocks consuming 122watts as GTX 780m does. First Kelper release where 600 series mobile flagship(680M) was a GTX 670 with much lower clocks. NVidia enhanced Kelper logic which improved clock speeds greatly- as demonstrated with 700 series and 800 mobile series. GTX 980m will be released in October. Kelper GTX 870m and 880m are rated for 25GLOPS/W.
For those interested- Sisoftware Sandra(TM) scientific aggregated ranking has new Maxwell card under "NVidia Graphics" near GK110 cards.