Based on the following needs, what solution should I choose for my client?

I have a client with less than 100 customers and less than 50 products. They would like to setup a customer login on their website. Customers should be able to login and see their last order (or perhaps last couple of orders). They can then change the quantity or simply re-order. If the price has changed since their last order, the total should auto update on the new order. Once they submit the order, an e-mail should be sent to the sales rep who will then call them to confirm and make payment arrangements over the phone.

Surely there is a pre-existing solution out there that could simply be customized to fit our needs. Any suggestions?

A little more info...

Forget about their current system as it is simply a phone call.
We will be setting up each customer account and manually entering their most recent order into whatever solution we decide to go with. From that point forward, the customers will be ordering through the website.

Therefore I am all about picking a shopping solution that includes the functionality that we want. I have little to no shopping cart experience so it is at this point I will open it up to suggestions. Open Source would be nice bu we are more than happy to pay if that is what it takes.

Many shopping cart systems can handle order and shippment tracking. A good free one that we and most hosts support is Zen Cart. Quick Shopping Cart is also a good one.

A couple of questions need to be considered before an accurate suggestion can be made: What is your budget, and what scripting language do you prefer (e.g., php or asp.net)?

PHP is the preferred scripting language. The budget is extremely flexible.

Obviously, open source is free. So a pay-for solution would need to have a tremendous upside to justify the cost? I would be willing to pay for a superior product.

Of the php-based carts I am familiar with I would recommend Zen Cart. If you need some unique functionality that is not included you can build or buy a module for that, including hiring an inexpensive developer for it.

You could look into an epos system. A point of sale system that is specifically designed for an e-commerce environment. I agree that you may be able to find these functions in a shopping cart as well!

Good Luck
Alexis

Sounds to me you would be best suited with a custom solution for this. Any good programmer can save order info, perform a recall of orders on customers login make changes for a new order then process the re-order.

Personally I do not like PHP and prefer .NET.