If you really want to go to a 205, the 50-series is definitely the way to go. I can't imagine you'ld ever notice a difference in fuel economy. The worn-out 195/55s you've got on there now may very well be smaller than new 205/50s would be anyway.
I've got a '99 SiR, and have been happy to stick with 195/55s on the stock rims. Kumho 712s for me, but Hankook also makes a V-rated tire in that size that is supposed to be a decent performer. As you mentioned, the AVS ES 100 is also a good value. If you really want to go nuts, look into the new Toyo T1-R. It's also available in a 195/55R15.
There's other choices in that size as well, but the above four are the ones I'd be considering.