When looking for a provider of software whether it is a prebuilt cart or a custom job be sure to check references extensively. Look at existing portfolios including talking to the owners if possible. There's a lot of suggestions here and all are valuable but I will tell you first and foremost find a good system and go with it. It won't be perfect out of the gate and it doesnt have to be. There were tons of perfect stores opening in 2001 and they were all out of business pretty quickly. Those that do, can, those that will often fail.