I would also like to add based on "redisigning our existing system". Do you mean where you work wrote the original software and sells it, or is it what you use at your business? If you don't plan on marketing your software beyond your company, why write it in the first place? You will spend years writing what you could purchase from an existing software vendor for far less than the cost of time it would take to write. Expecialy when you ask what to write it in.
Tom