Ok on the Shutter Speed issue.
I'm using 50mm F1.8, EFS 15-85 F3.5-5.6 mostly. Sometimes I want to play with the ISO but up to 800 max before I find the pictures unsable. So a higher ISO will be nice in my opinion, using f1.8 might cause blur or OOF if my hands are shaky.
Chasing after Higher ISO will bring you nowhere....Every newer generation of camera will bring about better/cleaner higher ISO. If you are really dying to upgrade to use higher ISO, go either newer XXXD/XXD (and upgrade every year, pain every year) or FF (do it once...but quite painful).
FF may be able to give you clean images at 6400 while crop may have issues getting it clean at 3200. So it's up to you to define how clean you want the images to be and how much you want to spend on a hobby.