I am not sure if it is a viable option for you, but we are of similar size, although our phone usage is a little higher, and we have a partial T1. Our phones and data come in together from a CLEC. The only downside that we have seen is that our data speed slows down a bit when our phone lines are all in use, but that is not a significant problem. I have also been told that this is how the partial T1 is set up. We set it to make voice the priority in heavy usage situations. All of our services are on one bill and are a LOT lower than what you are paying, even with our data tied into the bill.
Last, we do also have one POTS for our alarm and as an emergency back-up in case the T1 fails. We did have to rely on this one line for one entire day once last year because our T1 went down.
I do have to say that we were lucky in that we have a very reputable and competent CLEC locally to buy this service from.
