so I decided to spend a remarkably modest $230 (plus shipping) on the step-up Samsung CLP-620ND
Did you look into your cost per page for this printer? Buy your genuine Samsung toner from Amazon, you'll be paying nearly 13 cents per page for toner. Best price I found (cursory search on eBay, you may be able to do better) comes out at six cents a page. That's not horrific, but it's still more than twice the cost per page of your CLP-315.
Print 200 pages a week, and your best toner cost comes out at $624 per year. Looks like NewEgg would cost you $1040. Amazon's toner will set you back $1352. These prices do not include shipping. Makes that $230 initial cost look a little less inviting.
tanstaafl.