Dynavector XV-1S ---is it overkill for my system?

It is not overkill. You will hear a definite improvement with the XV-1s. However, the lack of easy VTA adjustment in the Classic 1 tonearm limits your ability to fine tune playback for different slabs of vinyl, which the XV-1s will readily reveal. Still, for whatever weight record you choose to adjust the arm to, you will get improved results over your current 17D3.

Your question is impossible to answer, given its subjective nature, but I have grown to believe that, if you think your tonearm is a weak link, buy a better tonearm FIRST. It will make your 17D3 sound better, if it's well matched in terms of effective mass, AND you will have it on hand when later you wish to upgrade the cartridge. In other words, a "good" cartridge will sound better in a great tonearm. A "great" cartridge will be held back by a merely good tonearm. (This is not to cast any judgement on the Classic tonearm, about which I know nothing; I am drawing on your own apparent opinion that it may be a weak link.)

Rushton---thanks for your response, I wouldn't miss not having easy VTA adjustment, I don't miss it now and frankly I have no desire to adjust VTA for different LPs, that's way too anal retentive for me! By the way, I forgot to mention my musical preferences are 60's and 70's psych and progressive rock, soul and funk, jazz, afrobeat, latin, etc. I'm sure this would have an influence on my choice of cartridge.