Been down this road many times.
You have a few options:
1. Technology Conepts (
www.techconcepts.co.za) offering called 'channel bonding', good speeds, however a few catches:
- They route through Verizon and more recently IS. If those ISP's are having conectivity problems you're buggered.
- They dont have a usage based model, so if you take out a 50Gb package and only use 30Gb, the remaining 20Gb's arent carried over.
2. RouterOS setup with routing ( dont know much about this option)
3. FreeBSD solution called Pfsense (
www.pfsense.org) I currently use this in my JHB and CT offices. 8 DSl lines in JHB and & 6 in CT, great load balancing function as wel as many other features.
4. Draytek manufacture a Load balancer (Vigor 3300v) that aggregates 4 WAN connections. Good box, Simple GUI, though not as many features as Pfsense
Lemme know if you would like more info.