Fits between HD 4830 and HD 4850
The Guru3D crew managed to get their hands on ATI's RV740 engineering release card and do a decent performance preview of it. As you probably already know, this is the first card made in the new 40nm manufacturing process and it's ATI's successor to the RV730 (Radeon HD 4650/4670). As such, this card is going to be a mainstream product and it should be priced at US $99/€89.
This engineering sample works at 650MHz for the core and features 640 stream processors, 32 texture memory units (TMUs) and 8 render output units, also known as ROPs. The interesting thing is that it will use GDDR5 memory which is paired up with a 128-bit memory interface. This should give this card performance similar to a card with GDDR3 memory paired up with a 256-bit memory interface.
According to the tests done at Guru3D with this engineering sample card and internal beta drivers, this card does exactly what it should - brings performance close to a Radeon HD 4850 for under 100 bucks. Of course, Guru3D's Hilbert Hagedoorn was eager to note that we are looking at an early sample and that final specifications might be a bit different.
In any case, ATI's RV740, probably known as the Radeon HD 4750, is a great chip and will probably offer the best bang for buck once it shows up in retail sometime in April.