What is something I can do on both improving the quote speed and the order execution speed that isn't terribly expensive and user friendly
STI is single threadded (as many execution systems are) and it also only publishes quotes every 100ms. I believe that is a system limitation that you are going to be stuck with. I assume you are using the API (automated). If so you can purchase 3rd party data (get quotes from Bloomberg/Activ/DTN) which will be streaming versus every 100ms. That will improve your data and then you can simply execute through the STI API.