That's not it as late September a 1 GB version of the Radeon HD 4670 will be released as well with a 750 core clock frequency and 1800 MHz GDDR3 memory, again 1 GB. Radeon HD 4650 (RV730Pro) at 74 USD GDDR3.Mind you that AMD will also introduce a lot of variations in the 4600 series as you'll spot:

So here's a good comparison scaled over the newer and older products. That reeks of a good performance per watt. Some interesting facts the uber low-end 4500 cards will consume less than 25 Watts of power ! The 4600 series will remain below 70 Watts, in fact you don't even need to connect them to your PSU's 6-pin power connector. The entry-level 4500 based product will have 80 Shader (Stream) processors, all 4600 series products will have a far nicer 320 Shader processors. From top to bottom these products will all be based on a 146 mm2 55nm chip, with the UVD 2.0, DirectX 10.1 and 8 channel sound through HDMI. Within these two lines you'll see a lot of products. So AMD is working on two new product series, the Radeon HD 4500 and Radeon HD 4600 product line. Though most products are still disclosed, I will give you a little bit of a preview what AMD is working on.

There will be a multitude in variation across the budget from a low-end to mid-range segment. AMD today announces the Radeon HD 4670 but is actually releasing a couple of products this month.

Ati radeon hd 4600 driver updates