The best way to ensure that you aren't leaving anything on the table is use a broker who knows the service providers and knows how to get you as much as possible.
Providers have become extremely competitive and one of the ways they are trying to attract customers is by making the start-up process as simple as possible. Service providers have tried many different methods of attracting customers and simplifying the start-up process.
Credit checks have been simplified, application paperwork been reduced in size, and there are increasingly discounts available for new customers. The free router when from a special promotion offered to increase month end sales to becoming a standard part of the product offering. It is now the exception to the norm to find providers that do not offer a router with their service.
In a buyers market remember that you can push and probably get concessions from the carrier but also remember that all carriers are not created equally. Several carriers might appear to offer a bargain price but you may be several hops from the internet and have a problem with latency. You may also be using a small carrier that hasn't actually checked the capacity of the CO before you sign your contract and can't even deliver the service they promised.
The only way that you will discover this is when you start using your connection and find that at peak traffic times your connection is bogged down at a level below that which was guaranteed. An additional advantage is that you will have the peace of mind knowing that you have an SLA and the company will deliver what you believe you will get.
If you are in the market of a DS3, communications are vital to your company. You should make sure you get both a reliable product and the price that you are looking for.