RB/5EX and throughtput limits

Got a problem with with a backup application – it is using all the bandwidth between main site and DR site.

4 separate networks, 1 connection to the ext firewall, and 1 for the connection between the two sites for a total of 6 networks.

Was going to put a mikrotik RB/5EX device at each site and limit the bandwidth between the two IP’s associated with the backup app.

One of my coworkers responsible for the actual purchase of the equipment was told by a distributor that the RB/5EX could not handle more than 33MB/s and therefore won’t work in this scenario - DS3 link.

Is this true???
If so can anyone think of a better solution, that costs less than a cisco 3800?

Thanks in advance,
Eric