I also owns a 2006 Esteem. before checking out Alternator upgrade options, Check out the battry first.could you please tell what is the Age of your car battery and what is your car usuage status?I expect battery is stock specification.
Why i am asking to checkout battery?-I had the same experince of yours. I am using car only on weekends and once even without usuage for 2 weeks my car got started in the first crank itself with the more than 3 years old battery and after running the car for more than 20 kms with ac and stereo, in a traffic block car engine got off and it was not starting. We had to push start the car and after 1hour when i checked up the car at Bosch service center, their battery checking tool shown that "Replace the battery" message. But at that time car was starting in the single crank and we even repetadly tried 7/8 times but battery didnt shown any issue. One of the shell was weak on that abttery. I had replaced that battery with a new bosch one at that day and car has no issues till now. I had installed Sub woofer and amp later and sometimes i wont use car for more than 2 weks. But still it has no problem and the charge indicater on the battery still shows green colour. Our fellow TAIan Varun suggested a battery upgarde for my car withour upgarding the alternator for a better performance. You can check out his battery upgrade on his thread. My Modified Maruti 800.
Jerks at the lower RPM range is a charecter of this car i guess. My car has this issue still even after replacing the clutch disc. What is your cars total running till now? Did you repleced your clutch disc earlier?I guess it is the time to replace the clutch disc.