A Taiwanese website published the first photo's and benchmarks on the Radeon HD 5750 which supposably is released half October,. The 5700 series cards should have 1120 Stream processors.
According to the Taiwanese forum poster the card indeed has 1120 stream/shader cores which means there would be 14 SIMD clusters on-board. The memory bus has been cut down from 256-bit towards 128-bit, yet much like the 4770 it's gDDR5 doubling up that bandwidth again. The memory is clocked at a spicy 4600 MHz accounting for 74 GB/sec of memory bandwidth. The GPU itself on this 5750 model was clocked at 700 MHz.
The benchmarks this guy included are not really representable nor stable. The card shows the same performance as a GTS 250 in 3DMark06, which doesn't seem right.
Judging from the photo's the card again has two DVI , HDMI and a displayport connector, so we can safely assume that the 5700 series will have Eyefinity support as well. power wise we see only a 6-pin power header meaning that the board definitely uses less than 150 Watt of current. Prices will be expected to be roughly 150 USD for this 5750 model and 200 USD for the 5770.