You can run Chrome as one thread, but I wouldn't recommend it, using this flag:
-single-process
Both browsers are good and it is a matter preference. I use chrome because it is easier for me.
As far as AMD vs. Intel and nVidia vs. ATI, I had to go with nVidia and Intel. I use a lot of OpenGL in Linux and need the performance there. Unfortunately, ATI's "open" hardware lacks matching nVidia's proprietary driver. Ideally, I would like to run AMD with nVidia, but you really get robbed of feature set this way. There are very few motherboards with an nVidia/AM3 chipset that also have USB 3.0 and SATA III. For future proofing and instant gradification, I've sold my soul and run i7 w/GTX 570.