extra screens for iMac (late 2013)

I have two screens hooked up to my iMac now but want to add another for a total of 4 screen. Can my iMac handle that and what gear do I need to hook up the extra one I want?

my iMac is running

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3.1 GHz Intel Core i7

16 GB 1600 MHz DDR3

NVIDIA GeForce GT 750M 1024 MB

OS X 10.9.5 (13F34)

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I have a Samsung 52 inch LED TV hooked up via thunderbolt and an Asus 21 inch hooked up via thunderbolt.

The only ports left open are two USB ports. I want another Asus 21 inch monitor.

Any help, please.