Re: 32 bit vs 64 bit??
With the apps you mention go for 64 bit. I have 3 GB ram and an AMD Athlon X2 3800+.
I am running all the applications you mention a lot on 64 bit on jaunty and hardy. Karmic will be OK as well. (I am running ubuntu, not ubuntu studio but the installation of the apps should be the same).
For blender I use the version that I download directly from the blender site. No install needed. Just extract the downloaded file and run the blender executable in the extracted file. If blender does no have sound then start it with "blender -g noaudio"
AMD64X2 3800+ 3GB Ram: 11.10
ACER one T1810 : 11.10 64 bit