what you could do, in my opinion, is you could go for 1GB DDR5 edition, and save on the bucks. Or invest in a bigger cabinet. 3GB ddr5 will be a wastage.
ask around. i may be wrong.
1GB 7950 isn't available. In fact it is technically impossible. Reason:
7950 has a 384 bit memory bus.
Which means each memory module is accessed via a 32 bit bus and there are 12 such modules to give a net bus width of 32 x 12 = 384bit.
Now in general memory modules have the capacity in powers of 2 i.e 64MB,128MB, 256MB....so on.
So twelve 64 MB modules will give a net memory of 64x12MB = 768MB
Similarly if each module is 128MB then net memory = 128 x 12 = 1.5 GB
7950 has twelve modules ,each of size 256 MB giving a net memory size of 3GB.
So the technically possible memory sizes for 7950 are 768MB, 1.5 GB , 3GB etc. Unfortunately only 3GB option is available in market.