I am a huge fan of Mikrotik. In the past, I have been worked for an ISP, and we made fantastic stuff with them. A CCR box that costs less than 1000€ can handle

I am a huge fan of Mikrotik. In the past, I have been worked for an ISP, and we made fantastic stuff with them. A CCR box that costs less than 1000€ can handle the same number of users, with advanced QoS queueing than an equivalent Cisco that costs 20x. Having (almost) the same features to ever model, from the big boxes to the core routers, it's a big plus, they are very flexible, and they have almost all the features that a carrier-class router needs (the big lack at that time were OSPF-v3 and multi-core BGP). Once you learn the CLI and some quirky configuration, it's worth the money. The only problem is the availability: they are not stable as a Cisco/Juniper, but you can add several layers of redundancy with a fraction of the costs. Also the support is very basic.