Any opinions out there on the relative merits of learning C++ in addition to C? Or, more broadly, on the requisite suite of software skills for any self-respecting quant?

My impression is that C++ skills are required in about 60-70 % of quant job postings, and general programming skills in either of C,C++, Matlab, Mathematica are required in 95 % of postings.

VBA might also be a useful skill to have up your sleeve in order to build desktop applications in the "Office" environment very quickly, producing readable but non-optimally performing applications. As for C vs C++, if you have C++, C is easy, though it might feel clumsy. If you have C, then C++ feels kind of familiar, but you probably need to do some work on object oriented programming in order to get the full benefits. It is however possible to write quick and dirty C++ programs that are basically C with a few C++ functions that you have learnt out of a book, then compile then using a C++ compiler (e.g. MS Visual C++) and run them OK.

Thank you very much for the helpful input. However, I am still unclear as to a practical path of study. I am already somewhat familiar with VBA and can practically apply this to my day-to-day spreadsheet work in Excel. Where should I start? What next? VBA > C > C++ > C# > VB .Net? What is a sensible sequential path? How would you prioritize these skills from a practical standpoint? Would you exclude anything? Any advice / guidance much appreciated.

Don't bother with learning C as a stepping stone to C++. Go straight to C++, there are plenty of courses and books for beginners without any C. FWIW stop at C++ as well. I am not sure how much C# is used in our little corner of the world. My opinion on C# is to remember that # is call the hash symbol, and that with a little loose pronunciation, C# becomes C'ash, which is what we have to spend to get and implement a new programming language.