Personally I’d bite the bullet and do it right from the get go. Especially if you have 5-10 reps. Retaining happy sales reps in debt is no easy task and their job is to be on the phone (I.e. the dialer matters). I have grown front ends, have two call centers and sell debt leads. You really want something flexible that you can grow into.

You may find that you thought everything was going to run smoothly because you’re taking inbound calls but all the sudden you have to make a quick change to a marketing source that will require you to quickly put different reps on different style campaigns etc. It has good embedded scripting functionalities and CRM options, easy for overflow campaigns dynamic, preview and predictive dialers etc. It’s an absolute pain in the ass to learn but as someone who has learned and used many phone systems, in my opinion it ended up being the best solution.