Still, trying to sort web traffic out by target IP address won't really work unless the target website exists in its own little bubble.
Realistically, if you want to make use of both routers, you'll probably have your internal hosts split up by VLAN, and have each VLAN's default GW address sitting on one of the routers, and make each router route for half the VLANs.
If your routers support VRRP, then great, you can make this work quite well, otherwise configuring some kind of resilience for your internet access could be a bit fiddly.