I am getting a red dot for sure.. I really want a large scope too, because they look damn good on the gun, and would give me a better base for some 100 yard target practice.
Something I really like is you can fit some lasers right in the hole for the fake gas tube. Some people think putting the cap for a fake gas tube there is a waste of time, but I like it, and I like it even more with a laser pointer fitted in there!
http://farm2.static.flickr.com/1031/4604882713_dd1a7170e7_o.jpg
http://i181.photobucket.com/albums/x154/back_marker/sig%20522/DSC_0092.jpg