Hmm well Im familiar with the FAB guards. I'm assuming you have the aluminum machined set. They are pretty well made and most people don't have anything bad to say. The only downside I can see to the aluminum FABs is that the do not allow a co-witness through the rear and front site (because the FAB guards sit high). Other hand guards, like troy, NEA, and Bonesteel Arms (what I use), sit much lower and allow the co-witness. So if you like the co-witness set up, you'll have to switch to one of these. If not, then the aluminum FABs will probably be fine.
The bushnell TRS is a good micro dot. You might also look at a Primary Arms and their microdot (which is similar to the TRS-25, although I like it a bit more). If you're going to stick with the FAB aluminum guards, you might also consider the Vortex Strikefire RED DOT (not the green/red), and use a medium scope ring.
Kolme