Tweak asterisk for voice traffic

I’m learning the hard way that many routers can’t handle voip traffic and don’t work with voice when connected to an asterisk machine. Is there a way to tweak asterisk to make it more ‘crap-router’ friendly? or is it just a case of finding another (affordable) router? if so is there a known cheap router that will work ok? I use cisco 2600 routers and swear by them but they have fans and the noise they make is unsuitable for some locations. Every other router I’ve tried doesn’t work with asterisk.

Turn off SIP ALG on the router, then do a standard NAT configuration on Asterisk. If there is no NAT, the router should be transparent, except for any prioritisation.