NVIDIA would be launching two mid-range SKU's, GeForce GTX 660 and GTX 650 in September along with the GTX 660Ti in Mid-August.
The GeForce GTX 660Ti would be based on the GK104 die featuring 1344 Cores, 2GB GDDR5 (192-bit) memory and a core/boost clock of 915MHz/980MHz. Factory overclocked models are expected to hit retail at launch for a premium over the reference price of $299.
It is expected that within a month later we would see two more mid-range cards, The GTX 660 (non-Ti) for instance features 1152-960 Cores (GK104) with core clock of 980MHz. The memory would remain 2GB along a 192-bit interface running at 6Ghz effective speed. Its expected price range is $229.
Finally, GTX 650 which is a rebadged GT 640 with GDDR5 memory and improved clocks would hit the market shelves at a price range of $189-$199. Featuring the same Gk107 core with 384 cores though faster clocks beyond 1GHz and a 5GHz clock 1GB memory would help it place a position over the GTX 550Ti.
Performance of the GTX 650 can be seen here while GTX 660Ti's full set of benchmarks can be seen here.