best byo modem for hfc and voip?

very recently switched from telstra to superloop after 10+ years. im on their lightspeed plan for what I was paying 50/20 to telstra. im on a hfc connection and get about 950 on my PC's ethernet and max 750 on wifi.

I'm quite pleased with my connection, but the zte h1600 modem i received from SL has a coverage range shorter than the modem I had with telstra and the speed tapers off to a sub-100 very fast. it's not that surprising, the router scores a measly 2/5 on whistle out.

i an aware that many rsps are restrictive with wan/phone configs but from the looks of things, superloop is very open with their network and voip since they gave me all the auth and config details for the VoIP as well as the WAN connection - so if I did have a byo modem I could set it up easily long as the gateway gives me enough permissions.

for now ill use my tp link extender since I've already been charged for the new modem. but for later..

could you guys suggest me a byo modem supporting VoIP with better range and stronger signal?

edit: sorry I only thought of this after posting.

should I just get a router? if so what's good for less than 250 aud