Since you've got a FSP gas block, I would recommend something like a tube style red dot like an Aimpoint that had a single dot (I've got an Aimpoint CompC3 on the way [SWFA kit with everything needed for $400]). It should be a little further forward. I like my objective lens as close to the end of the upper receiver rail (before the foregrip) as I can get it, but you might like something a little more forward or back.
[BTW, I got the CompC3 due to the price/quality ratio. I don't feel that I will ever need to take the optic under more than 5 feet of water or attach night vision to it, so it didn't make any since to pay more for the Comp M3 or ML3. I also wanted a 2MOA dot for hunting.]
You'll probably want your optic a little high so the irons will be in the lower third of the optic for co-witnessing. I ran that before with an open style red dot and enjoyed it. If you plan to use the gun for multiple applications (I will use mine for whitetail and hogs), it gives you less interference with the sight picture and allows for better aiming IMO. They are both great sights, but I'm looking forward to being able to turn on my red dot and leave it on for a few years.
If I remember correctly, the XVEZ doesn't have any rail ahead of the front sight post since the EZ rail system is made to be a drop in for the standard M4 foregrip. You're a little lacking on rail space, so a vertical grip with a light built into it might be right up your alley. However, they don't run cheap. You could also do an offset or side mount on the side rails to hold a light. Just make sure whatever light you run is quick and easy to operate.
If you ever upgrade the rail to something longer with a hole for the FSP, you can mount the light ahead of it. That way everything is on top of the gun, leaving more space underneath for a standard rifle style grip.