Suggestions for type of service

I have a growing business with about 5 reps taking calls every day. Most are incoming calls but some are outgoing. My internet connection is cable, static IP, 5M down 1.5M up. VOIP traffic is shared with other internet traffic such as browsing and email. I’m spending about $350 per month on about 15,000 inbound minutes using g729 and Linksys/SPA942 IP phones. My Asterisk box is on a real IP (not behind NAT).

I’ve been through several SIP providers… the traceroute to my current provider is pretty good, but I’m still not thrilled with call quality. Fairly often I hear reps asking people to repeat themselves. I’m thinking that our VOIP traffic going over the public internet doesn’t help because there’s really no way to properly do end-to-end QoS.

I thought I’d ask for suggestions from the community about what type of service would best balance cost vs quality for someone in my situation. Any input is welcome (and I hope this is on topic).