How much armor rating can you get before hitting the cap? Keep in mind that I have a mod that allows me to get bonuses if I wear a full set excluding the helmet.

http://uesp.net/wiki/Skyrim:Armor

Because it'd be better to see for yourself, than try to explain it to you and be wrong.

667 is the armor cap. Wearing a full set of armor (boots, gauntlets, cuirass and helm) grants a 100-point hidden bonus (25 points for each piece) allowing you to hit the cap with a displayed armor rating of 567. Add 25 to that for each item you aren't wearing.