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I have no concrete evidence but I'd still say a resounding, "definitely NOT."

I run a 2011 13" MBP with a 21.5" Dell monitor and it seems to lag slightly just with that. I'd assume the new integrated HD 4000 graphics would help with single external montor lag, but not power a whole second one.
 
Can it be done? If so how and what will I need? Thanks for any advice in advance.

You can drive the second monitor via usb and some additional equipment. Do a google search.

I think the new rMBP can run 2 monitors directly as there are 2 display ports/thunderbolt connections.
 
I'm surprised by the problems you're having with a 21" as these machines are supposed to run a 27 tb display no problem.

I don't want to exaggerate my problem. It's barely even a lag, but still noticeable.
 
I think the new rMBP can run 2 monitors directly as there are 2 display ports/thunderbolt connections.

The new rMBP hast two TB ports and one HDMI port. I'm pretty sure you can use all three of them simultaneously. That's three external displays.
 
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