Map size help

Hey I was just wandering if anyone knows what the best mapsize and amount of Civs in a game would work best with my PC specs.
RAM: 6:00GB
Processor: Intel Core i3-2100 CPU @3.1GHz
System: Windows 7 64 bit
Graphics: Nvidia GeForce GTX 550 Ti
I tried playing on a huge map with 15 civs or something and during the modern era it was unbelievably slow (no surprises there) so I'm just wondering what's the largest map size and the most amount of civs I can have in a game without it dying on me during the modern era?
Thanks for the help.

Moderator Action: Moved to general discussion.

From what you describe, chances are very high it would be fine on large map.

And number of civs doesn't really matter by the time you get to modern era; the AIs are going to spam cities to take over the map.

Okay thanks for the help