I'm not sure I'd trust a carbon fiber handguard to be rigid enough to keep an IR laser zeroed. What's wrong with the 516 rail you have? Those are pretty sturdy. Plus, not buying a new one allows more money for the rest of your stuff, which is going to be hard enough to cram into your budget as it is.
Silencer=YHM turbo, that's for sure. Great performance at just about the cheapest price point in the industry. Order from Hansohn Brothers and contact them for an Arfcom discount. Even then, with the tax stamp, you're looking at about $600 or so, depending on your local transfer fees.
So the can eats up almost half your budget.
You could get the Steiner single spectrum IR dbal I2 for IR laser illuminator and pointer which is about $800. You could also just get an IR laser. TNVC has something coming out soon for ~$300. No illuminator, so you'd have to get a separate IR light. If you want to go cheap, you could probably get an IR flashlight or something off amazon and mount it with a scope ring. The Sionix Camera thread around here has some budget-focused IR solutions, you might want to check that thread out.
White light. Lots of options.