So, I bought a 41CV

[Dave Britten]

I highly recommend the Advantage ROM. It's a collection of the most important features from the 12C, 15C, and 16C.

Extended Functions is also worth having, even if you don't get a bunch of additional Extended Memory modules. You'll still get a bit of x-mem, plus quite a few useful functions.

Also, if you need a case, look at your preferred electronics retailer (Best Buy, etc.). Portable hard drive cases are often a very good fit. I have one with a padded interior, and a slot on the front that fits a few QRGs, overlays, and a tiny Moleskine for programs/notes.