If it is a true multiport server NIC with driver support for teaming for load sharing, and if your switch does support this kind of teaming as well, you may get a boost in case, that really the network connection is the bottleneck.
But this does not work with common cards and consumer grade network switches.
Are all devices connected via Gigabit network already?
Which CPU do you use and how much memory has your server?
Best greetings from Germany
Olaf