no you dont need a specific router to do that
as long as your ISP link is capable for doing so - ie. the same PPP account etc.
it will not work if you have 2 different links.
the simplest way to do is to put the linux router behind 2 modems in route-mode, so that the linux router can have an ethernet-based link (just for simplicity), and do the link aggregation/bonding.
modem1 --- |
linux --> doing ethernet-based port aggregation
modem2 --- |