For quick work I fire up my Silver A (2 burners so smaller than your S-320.) If it's charcoal, I recommend a 22 1/2" Weber kettle of some sort. The 18 1/2" is good but the extra space gives you bigger cooking zones (more coals to one side or either side with none in the middle.) The most common Smokey Joe is 14 1/2" but I think there is one that is 18 1/2".
I do my shopping on Craigslist because I prefer their pricing. :)
Edit: I just looked in Shreveport Craigslist and there's nothin!