If accurate, the dual-slot GTX 550 Ti is based on the 40nm GF116 GPU, featuring 192 CUDA cores, 32 texture units, and GPU/shader clocks of 900/1800MHz. It will also carry 1GB of GDDR5 memory with a 128-bit bus and an effective speed of 4100MHz, while peak power consumption is rated at 110W.
Pricing seems to start around €160 ($220), which puts the new mainstream card in the general vicinity of overclocked GeForce GTX 460s and the Radeon HD 6870. It's also just below the recently reviewed GTX 560 Ti, which uses Nvidia's GT114 GPU with double the CUDA cores and memory interface.
Spec-wise, the GF116 looks very similar to the GF106, which powered the last-gen GTS 450 (currently $120 before rebates). However, it seems Nvidia believes the new chip's speedier frequencies (900/1800MHz versus 783/1566MHz) grant it access to the GTX branding and inherently higher pricing.