Assuming that you will plug your OBi device into the router via an Ethernet cable, and not via WiFi, any current model router will work fine. You can simply plug things in and it'll work. If you do experience some packet loss or other issues caused by other things on your home network (LAN), you can enable QoS in the router, giving priority to the OBi's MAC address.
The router doesn't care that you are using SIP (well, Callcentric uses SIP, and Google Voice uses XMPP). The only thing you must do, is to check the router's instructions and menus, and if there is a "SIP ALG" setting, DISable that setting, as it interferes with your OBi device.
From a general, non-VoIP standpoint, consider that the model you mentioned is already outdated. It's cheap for that reason. If you can afford more, then buy a router that supports at least "AC 1900" or faster. In the real world, you may or may not notice a difference, depending on the age of your stuff that is using WiFi, but you will be investing in a router that has a longer useful lifespan.